{"segment":[{"time":24,"part":[{"title":"T\u00edch v\u00e0o \u00f4 \u0111\u00fang","title_trans":"","temp":"true_false","correct":[["t","f","f","f"]],"list":[{"point":5,"image":"","col_name":["Kh\u1eb3ng \u0111\u1ecbnh","\u0110\u00fang","Sai"],"arr_ques":["Th\u1eddi gian \u0111\u1ec3 m\u1ed9t \u00f4 t\u00f4 v\u01b0\u1ee3t qua qu\u00e3ng \u0111\u01b0\u1eddng AB t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi v\u1eadn t\u1ed1c c\u1ee7a \u00f4 t\u00f4 \u0111\u00f3","Chu vi c\u1ee7a m\u1ed9t h\u00ecnh vu\u00f4ng t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi \u0111\u1ed9 d\u00e0i c\u1ee7a c\u1ea1nh h\u00ecnh vu\u00f4ng \u0111\u00f3","\u0110\u1ea1i l\u01b0\u1ee3ng A t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi \u0111\u1ea1i l\u01b0\u1ee3ng B th\u00ec khi A gi\u1ea3m B c\u0169ng gi\u1ea3m","\u0110\u1ea1i l\u01b0\u1ee3ng A t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi \u0111\u1ea1i l\u01b0\u1ee3ng B th\u00ec khi A t\u0103ng B c\u0169ng t\u0103ng"],"explain":["Tr\u00ean qu\u00e3ng \u0111\u01b0\u1eddng AB, n\u1ebfu v\u1eadn t\u1ed1c t\u0103ng l\u00ean th\u00ec th\u1eddi gian \u0111i h\u1ebft qu\u00e3ng \u0111\u01b0\u1eddng gi\u1ea3m xu\u1ed1ng v\u00e0 ng\u01b0\u1ee3c l\u1ea1i. V\u1eady \u0111\u00e2y l\u00e0 quan h\u1ec7 t\u1ec9 l\u1ec7 ngh\u1ecbch.","<br\/>Chu vi h\u00ecnh vu\u00f4ng b\u1eb1ng \u0111\u1ed9 d\u00e0i m\u1ed9t c\u1ea1nh nh\u00e2n 4, n\u00ean \u0111\u1ed9 d\u00e0i c\u1ea1nh h\u00ecnh vu\u00f4ng t\u0103ng l\u00ean th\u00ec chu vi h\u00ecnh vu\u00f4ng c\u0169ng t\u0103ng. V\u1eady \u0111\u00e2y l\u00e0 quan h\u1ec7 t\u1ec9 l\u1ec7 thu\u1eadn.","<br\/>\u0110\u1ea1i l\u01b0\u1ee3ng A t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi \u0111\u1ea1i l\u01b0\u1ee3ng B th\u00ec A gi\u1ea3m l\u00e0m \u0111i cho B t\u0103ng l\u00ean v\u00e0 ng\u01b0\u1ee3c l\u1ea1i."]}]}],"id_ques":631},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[4]],"list":[{"point":5,"ques":" <span class='basic_left'>M\u1ed9t \u00f4 t\u00f4 \u0111i t\u1eeb A \u0111\u1ebfn B v\u1edbi v\u1eadn t\u1ed1c 50 km\/h v\u00e0 tr\u1edf v\u1ec1 A v\u1edbi v\u1eadn t\u1ed1c 60 km\/h. Bi\u1ebft th\u1eddi gian v\u1ec1 \u00edt h\u01a1n th\u1eddi gian \u0111i l\u00e0 30 ph\u00fat. T\u00ednh th\u1eddi gian \u0111i t\u1eeb A \u0111\u1ebfn B r\u1ed3i quay l\u1ea1i A?<\/span>","select":["A. 4 gi\u1edd ","B. 4,5 gi\u1edd","C. 5 gi\u1edd","D. 5,5 gi\u1edd "],"explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> X\u00e1c \u0111\u1ecbnh quan h\u1ec7 t\u1ec9 l\u1ec7 ngh\u1ecbch gi\u1eefa hai \u0111\u1ea1i l\u01b0\u1ee3ng. <br\/> Theo t\u00ednh ch\u1ea5t c\u1ee7a hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch l\u1eadp c\u00e1c t\u1ec9 s\u1ed1 b\u1eb1ng nhau $\\left(\\dfrac{x_{1}}{x_{2}} = \\dfrac{y_{2}}{y_{1}}\\right) $ <br\/><br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> <span class='basic_left'> \u0110\u1ed5i: 30 ph\u00fat = $\\dfrac{1}{2}$ (gi\u1edd) <br\/> Gi\u1ea3 s\u1eed \u00f4 t\u00f4 \u0111i t\u1eeb A \u0111\u1ebfn B v\u1edbi v\u1eadn t\u1ed1c 50 km\/h v\u1edbi th\u1eddi gian l\u00e0 $t_{1}$ (gi\u1edd), $t_{1} > 0$ <br\/> \u00d4 t\u00f4 tr\u1edf v\u1ec1 t\u1eeb B t\u1edbi A v\u1edbi v\u1eadn t\u1ed1c 60 km\/h v\u1edbi th\u1eddi gian l\u00e0 $t_{2}$ (gi\u1edd), $t_{2} > 0$ <br\/> Theo gi\u1ea3 thi\u1ebft c\u00f3: $t_{1} - t_{2} = \\dfrac{1}{2} $ <br\/> Tr\u00ean c\u00f9ng qu\u00e3ng \u0111\u01b0\u1eddng th\u00ec th\u1eddi gian v\u00e0 v\u1eadn t\u1ed1c l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch n\u00ean ta c\u00f3: <br\/> $ \\dfrac{50}{60} = \\dfrac{t_{2}}{t_{1}} \\Leftrightarrow \\dfrac{t_{1}}{6} = \\dfrac{t_{2}}{5} = \\dfrac{t_{1} - t_{2}}{6-5} = \\dfrac{\\dfrac{1}{2}}{1} = \\dfrac{1}{2} \\\\ \\Rightarrow t_{1} = 6.\\dfrac{1}{2} = 3 \\\\ t_{2} = 5.\\dfrac{1}{2} = 2,5 $ <br\/> V\u1eady th\u1eddi gian \u0111i t\u1eeb A \u0111\u1ebfn B r\u1ed3i quay l\u1ea1i A l\u00e0 : $t_{1} + t_{2} = 3 + 2,5 = 5,5 $ (gi\u1edd) <br\/><span class='basic_pink'> \u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 D. <\/span><\/span> ","column":2}]}],"id_ques":632},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"ques":"Bi\u1ebft $x, y$ l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch v\u00e0 c\u00f3 c\u00e1c gi\u00e1 tr\u1ecb t\u01b0\u01a1ng \u1ee9ng cho \u1edf b\u1ea3ng sau: <table><tr><td> x<\/td> <td> 4 <\/td> <td> 8<\/td><\/tr> <tr><td> y <\/td> <td> 6 <\/td> <td> ? <\/td><\/tr> <\/table> K\u1ebft qu\u1ea3 \u1edf \u00f4 tr\u1ed1ng l\u00e0: ","select":["A. 16","B. 24","C. 3","D. -36 "],"hint":"X\u00e1c \u0111\u1ecbnh h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 $a = xy$, sau \u0111\u00f3 thay v\u00e0o r\u1ed3i t\u00ecm $y$.","explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> X\u00e1c \u0111\u1ecbnh h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 a, v\u1edbi $a = xy$ <br\/> T\u00ecm $y$ theo c\u00f4ng th\u1ee9c: $ y = \\dfrac{a}{x} $ <\/span> <br\/><br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> V\u00ec $y$ v\u00e0 $x$ l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch n\u00ean h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 $ a = xy = 4.6 = 24$ <br\/> Khi $x = 8$ th\u00ec $ y = \\dfrac{a}{x} = \\dfrac{24}{8} = 3$ <br\/><br\/><span class='basic_pink'> \u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 C. <\/span><\/span> ","column":4}]}],"id_ques":633},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[4]],"list":[{"point":5,"ques":" <span class='basic_left'>Cho bi\u1ebft $y$ t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi $x$ theo h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 l\u00e0 0,8 v\u00e0 $x$ t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi $z$ theo h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 l\u00e0 0,5. Khi \u0111\u00f3, $y$ t\u1ec9 l\u1ec7 thu\u1eadn v\u1edbi $z$ theo h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 l\u00e0:<\/span>","select":["A. 0,625","B. 1,3 ","C. 0,4","D. 1,6 "],"explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> * N\u1ebfu \u0111\u1ea1i l\u01b0\u1ee3ng $y$ li\u00ean h\u1ec7 v\u1edbi \u0111\u1ea1i l\u01b0\u1ee3ng $x$ theo c\u00f4ng th\u1ee9c $y = \\dfrac{a}{x} $ hay $xy = a$ (a l\u00e0 m\u1ed9t h\u1eb1ng s\u1ed1 kh\u00e1c 0) th\u00ec ta n\u00f3i $y$ t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi $x$ theo h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 a. <br\/> * N\u1ebfu $y$ li\u00ean h\u1ec7 v\u1edbi $x$ theo c\u00f4ng th\u1ee9c $y = kx (k \\neq 0)$ th\u00ec $y$ t\u1ec9 l\u1ec7 thu\u1eadn v\u1edbi $x$. <\/span> <br\/><br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> Ta c\u00f3: $y$ t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi $x$ theo h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 l\u00e0 0,8 n\u00ean $y = \\dfrac{0,8}{x} $ (1) <br\/> $x$ t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi $z$ theo h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 l\u00e0 0,5 n\u00ean $x = \\dfrac{0,5}{z} $ (2) <br\/> T\u1eeb (1) v\u00e0 (2) c\u00f3: $y = \\dfrac{0,8}{\\dfrac{0,5}{z}} = 1,6 z$ <br\/> V\u1eady $y$ t\u1ec9 l\u1ec7 thu\u1eadn v\u1edbi $z$ theo h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 l\u00e0 1,6. <br\/><br\/><span class='basic_pink'> \u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 D. <\/span><\/span> ","column":2}]}],"id_ques":634},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"ques":" <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop7/toan/daiso/bai14/lv2/img\/D7C22-TB1-01.png' \/><\/center><span class='basic_left'> M\u1ed9t b\u00e1nh r\u0103ng c\u01b0a c\u00f3 20 r\u0103ng, quay \u0111\u01b0\u1ee3c 60 v\u00f2ng trong 1 ph\u00fat. N\u00f3 kh\u1edbp v\u1edbi m\u1ed9t b\u00e1nh r\u0103ng c\u1eeda kh\u00e1c c\u00f3 $x$ r\u0103ng. Gi\u1ea3 s\u1eed b\u00e1nh r\u0103ng c\u01b0a th\u1ee9 hai quay \u0111\u01b0\u1ee3c $y$ v\u00f2ng m\u1ed9t ph\u00fat . H\u00e3y bi\u1ec3u di\u1ec5n $y$ qua $x$. <\/span>","select":["A. $y = 80x$ ","B. $y = 1200x$ ","C. $y = \\dfrac{1200}{x} $ ","D. $y = \\dfrac{x}{1200} $ "],"explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> X\u00e1c \u0111\u1ecbnh quan h\u1ec7 t\u1ec9 l\u1ec7 ngh\u1ecbch gi\u1eefa hai \u0111\u1ea1i l\u01b0\u1ee3ng. <br\/> Theo t\u00ednh ch\u1ea5t c\u1ee7a hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch l\u1eadp c\u00e1c t\u1ec9 s\u1ed1 b\u1eb1ng nhau $\\left(\\dfrac{x_{1}}{x_{2}} = \\dfrac{y_{2}}{y_{1}}\\right) $ <br\/><br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> Trong c\u00f9ng m\u1ed9t th\u1eddi gian th\u00ec s\u1ed1 r\u0103ng c\u01b0a v\u00e0 s\u1ed1 v\u00f2ng quay l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi nhau, do \u0111\u00f3: <br\/> $ \\dfrac{20}{x} = \\dfrac{y}{60} \\Rightarrow y = \\dfrac{20.60}{x} = \\dfrac{1200}{x} $ <br\/><br\/><span class='basic_pink'> \u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 C. <\/span><\/span> ","column":2}]}],"id_ques":635},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[4]],"list":[{"point":5,"ques":" <span class='basic_left'> Bi\u1ebft 78 ng\u01b0\u1eddi ho\u00e0n th\u00e0nh m\u1ed9t c\u00f4ng vi\u1ec7c trong 65 ng\u00e0y. N\u1ebfu c\u1ea3i ti\u1ebfn c\u00f4ng c\u1ee5 \u0111\u1ec3 n\u0103ng su\u1ea5t lao \u0111\u1ed9ng t\u0103ng th\u00eam 20% th\u00ec c\u1ea7n gi\u1ea3m bao nhi\u00eau ng\u01b0\u1eddi m\u00e0 v\u1eabn ho\u00e0n th\u00e0nh c\u00f4ng vi\u1ec7c \u0111\u00f3 trong 65 ng\u00e0y? <\/span>","select":["A. 10 ng\u01b0\u1eddi ","B. 11 ng\u01b0\u1eddi ","C. 12 ng\u01b0\u1eddi ","D. 13 ng\u01b0\u1eddi "],"explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> X\u00e1c \u0111\u1ecbnh quan h\u1ec7 t\u1ec9 l\u1ec7 ngh\u1ecbch gi\u1eefa hai \u0111\u1ea1i l\u01b0\u1ee3ng. <br\/> Theo t\u00ednh ch\u1ea5t c\u1ee7a hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch l\u1eadp c\u00e1c t\u1ec9 s\u1ed1 b\u1eb1ng nhau $\\left(\\dfrac{x_{1}}{x_{2}} = \\dfrac{y_{2}}{y_{1}}\\right) $ <br\/><br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> <span class='basic_left'> C\u00f9ng m\u1ed9t c\u00f4ng vi\u1ec7c v\u00e0 s\u1ed1 ng\u00e0y l\u00e0m vi\u1ec7c nh\u01b0 nhau th\u00ec n\u0103ng su\u1ea5t lao \u0111\u1ed9ng v\u00e0 s\u1ed1 ng\u01b0\u1eddi l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch. Ta c\u00f3: <table><tr><th><\/th><th>N\u0103ng su\u1ea5t lao \u0111\u1ed9ng<\/th><th>S\u1ed1 ng\u01b0\u1eddi<\/th><\/tr><tr><td>L\u00fac tr\u01b0\u1edbc<\/td><td>100%<\/td><td>78<\/td><\/tr><tr><td>L\u00fac sau<\/td><td>120%<\/td><td>$x$<\/td><\/tr><\/table> Theo t\u00ednh ch\u1ea5t c\u1ee7a \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch ta c\u00f3: <br\/> $\\dfrac{100}{120} = \\dfrac{x}{78} \\Rightarrow x = \\dfrac{100.78}{120} = 65 $ <br\/> V\u1eady khi c\u1ea3i ti\u1ebfn c\u00f4ng c\u1ee5 \u0111\u1ec3 n\u0103ng su\u1ea5t lao \u0111\u1ed9ng t\u0103ng 20% th\u00ec ch\u1ec9 c\u1ea7n 65 ng\u01b0\u1eddi \u0111\u1ec3 ho\u00e0n th\u00e0nh c\u00f4ng vi\u1ec7c. <br\/> V\u1eady s\u1ed1 ng\u01b0\u1eddi c\u1ea7n gi\u1ea3m l\u00e0: 78 - 65 = 13 (ng\u01b0\u1eddi). <br\/><span class='basic_pink'> \u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 D. <\/span><\/span> ","column":2}]}],"id_ques":636},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":5,"ques":"Cho bi\u1ebft hai \u0111\u1ea1i l\u01b0\u1ee3ng $x$ v\u00e0 $y$ t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi nhau. C\u00f4ng th\u1ee9c li\u00ean h\u1ec7 gi\u1eefa $x$ v\u00e0 $y$ l\u00e0: <table><tr><td>$x$<\/td><td>$\\frac{1}{6} $<\/td><td>-1<\/td><td>0,(12)<\/td><\/tr><tr><td>$y$<\/td><td><\/td><td><\/td><td>8,25<\/td><\/tr><\/table> ","select":["A. $xy = -1$ ","B. $xy = 1$","C. $y = -x $","D. $\\dfrac{y}{x} = 1 $ "],"explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> $x$ v\u00e0 $y$ l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch n\u00ean $x$ v\u00e0 $y$ li\u00ean h\u1ec7 v\u1edbi nhau b\u1edfi c\u00f4ng th\u1ee9c: $y = \\dfrac{a}{x} $<\/span> <br\/><br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> $x$ v\u00e0 $y$ l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch. <br\/> \u1ede c\u1ed9t cu\u1ed1i ta t\u00ednh \u0111\u01b0\u1ee3c h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 $a = x.y = 0,(12) . 8,25 = \\dfrac{12}{99}.8,25 = 1 $<br\/> V\u1eady c\u00f4ng th\u1ee9c li\u00ean h\u1ec7 gi\u1eefa $x$ v\u00e0 $y$ l\u00e0 : $y = \\dfrac{1}{x} $ hay $xy = 1 $ <br\/><br\/><span class='basic_pink'> \u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 B. <\/span><\/span> ","column":4}]}],"id_ques":637},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":5,"ques":"<span class='basic_left'> Cho $y$ v\u00e0 $x$ l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch, bi\u1ebft r\u1eb1ng khi $x = -4$ th\u00ec $y = -8$. C\u1ed9t n\u00e0o sau \u0111\u00e2y sai?<\/span> <table><tr><th>C\u1ed9t<\/th><th>1<\/th><th>2<\/th><th>3<\/th><th>4<\/th><th>5<\/th><\/tr><tr><td>$x$<\/td><td>-8<\/td><td>-2<\/td><td>-4<\/td><td>2<\/td><td>8<\/td><\/tr><tr><td>$y$<\/td><td>-4<\/td><td>-16<\/td><td>-8<\/td><td>16<\/td><td>6<\/td><\/tr><\/table>","select":["A. C\u1ed9t 4","B. C\u1ed9t 5 ","C. C\u1ed9t 1 ","D. C\u1ed9t 2 "],"hint":"T\u00ednh h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 $a = xy$ c\u1ee7a t\u1eebng c\u1ed9t r\u1ed3i so s\u00e1nh. ","explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> X\u00e1c \u0111\u1ecbnh h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 a, v\u1edbi $a = xy$ .<\/span> <br\/><br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> V\u00ec $y$ v\u00e0 $x$ l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch n\u00ean $a = xy = (-4).(-8) = 32 $ <br\/> \u1ede c\u1ed9t 5 c\u00f3 $x.y = 8.6 = 48 \\neq 32$ <br\/> C\u1ed9t sai l\u00e0 c\u1ed9t 5. <br\/><br\/><span class='basic_pink'> Ch\u1ecdn \u0111\u00e1p \u00e1n B. <\/span><\/span> ","column":4}]}],"id_ques":638},{"time":9,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["3"]]],"list":[{"point":5,"width":50,"type_input":"","ques":"<span class='basic_left'>\u0110\u1ec3 ho\u00e0n th\u00e0nh m\u1ed9t c\u00f4ng vi\u1ec7c c\u1ea7n 12 ng\u01b0\u1eddi l\u00e0m trong 10 ng\u00e0y. N\u1ebfu mu\u1ed1n l\u00e0m xong s\u1edbm 2 ng\u00e0y th\u00ec c\u1ea7n \u0111i\u1ec1u \u0111\u1ed9ng th\u00eam bao nhi\u00eau ng\u01b0\u1eddi? (v\u1edbi n\u0103ng su\u1ea5t nh\u01b0 nhau) <br\/> \u0110\u00e1p s\u1ed1: $\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}$ (ng\u01b0\u1eddi)<\/span>","hint":"B\u01b0\u1edbc 1: T\u00ednh s\u1ed1 ng\u01b0\u1eddi c\u1ea7n thi\u1ebft \u0111\u1ec3 l\u00e0m vi\u1ec7c trong 8 ng\u00e0y. <br\/> B\u01b0\u1edbc 2: Suy ra s\u1ed1 ng\u01b0\u1eddi c\u1ea7n \u0111i\u1ec1u \u0111\u1ed9ng th\u00eam. ","explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> X\u00e1c \u0111\u1ecbnh quan h\u1ec7 t\u1ec9 l\u1ec7 ngh\u1ecbch gi\u1eefa hai \u0111\u1ea1i l\u01b0\u1ee3ng. <br\/> Theo t\u00ednh ch\u1ea5t c\u1ee7a hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch l\u1eadp c\u00e1c t\u1ec9 s\u1ed1 b\u1eb1ng nhau $\\left(\\dfrac{x_{1}}{x_{2}} = \\dfrac{y_{2}}{y_{1}}\\right) $ <br\/><br\/>T\u00f3m t\u1eaft \u0111\u1ec1 b\u00e0i: <br\/> S\u1ed1 ng\u00e0y l\u00e0m $ \\hspace{1cm} $ S\u1ed1 ng\u01b0\u1eddi l\u00e0m <br\/> 10 ng\u00e0y $ \\hspace{1,8cm} $ 12 ng\u01b0\u1eddi <br\/> 8 ng\u00e0y $ \\hspace{2cm} $ $x$ ng\u01b0\u1eddi? <br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> V\u1edbi c\u00f9ng m\u1ed9t c\u00f4ng vi\u1ec7c th\u00ec s\u1ed1 ng\u00e0y l\u00e0m v\u00e0 s\u1ed1 ng\u01b0\u1eddi l\u00e0m l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch. <br\/> Theo t\u00ednh ch\u1ea5t c\u1ee7a hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch, ta c\u00f3: <br\/> $\\dfrac{10}{8} = \\dfrac{x}{12} \\Rightarrow x = \\dfrac{10.12}{8} = 15 $ <br\/> Suy ra: C\u1ea7n 15 ng\u01b0\u1eddi \u0111\u1ec3 ho\u00e0n th\u00e0nh c\u00f4ng vi\u1ec7c trong 8 ng\u00e0y. <br\/> V\u1eady s\u1ed1 ng\u01b0\u1eddi c\u1ea7n \u0111i\u1ec1u \u0111\u1ed9ng th\u00eam l\u00e0: $15 - 12 = 3$(ng\u01b0\u1eddi) <br\/><span class='basic_pink'> \u0110\u00e1p s\u1ed1 l\u00e0 3. <\/span><\/span> "}]}],"id_ques":639},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[4]],"list":[{"point":5,"ques":" Cho $y$ v\u00e0 $x$ l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch. C\u1ed9t n\u00e0o sau \u0111\u00e2y sai? <br\/> <table><tr><th>C\u1ed9t<\/th><th>1<\/th><th>2<\/th><th>3<\/th><th>4<\/th><\/tr><tr><td>$x$<\/td><td>3<\/td><td>2<\/td><td>5<\/td><td>6<\/td><\/tr><tr><td>$y$<\/td><td>10<\/td><td>15<\/td><td>6<\/td><td>6<\/td><\/tr><\/table>","select":["A. C\u1ed9t 1","B. C\u1ed9t 2 ","C. C\u1ed9t 3 ","D. C\u1ed9t 4 "],"hint":"T\u00ednh h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 $a = xy$ c\u1ee7a t\u1eebng c\u1ed9t r\u1ed3i so s\u00e1nh. ","explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> X\u00e1c \u0111\u1ecbnh h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 a, v\u1edbi $a = xy$ .<\/span> <br\/><br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> V\u00ec $y$ v\u00e0 $x$ l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch n\u00ean $a = x_{1}y_{1} = x_{2}y_{2} = x_{3}y_{3} = x_{4}y_{4}$ <br\/> C\u1ed9t 1: $ x_{1}y_{1} = 3.10 = 30 $ <br\/> C\u1ed9t 2: $ x_{2}y_{2} = 2.15 = 30 $ <br\/> C\u1ed9t 3: $ x_{3}y_{3} = 5.6 = 30 $ <br\/> C\u1ed9t 4: $ x_{4}y_{4} = 6.6 = 36 $ <br\/> C\u00f3 $36 \\neq 30$. V\u1eady c\u1ed9t sai l\u00e0 c\u1ed9t 4. <br\/><br\/><span class='basic_pink'> \u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 D. <\/span><\/span> ","column":4}]}],"id_ques":640},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":5,"ques":"M\u1ed1i quan h\u1ec7 gi\u1eefa hai \u0111\u1ea1i l\u01b0\u1ee3ng $x$ v\u00e0 $y$ cho trong b\u1ea3ng l\u00e0: <table> <tr> <td> $x$<\/td> <td> $\\frac{1}{2} $<\/td> <td> 1<\/td> <td> 2<\/td> <td> 4 <\/td><\/tr> <tr> <td> $y$<\/td> <td> $1\\frac{1}{2} $<\/td> <td> 3<\/td> <td> 6<\/td> <td> 12 <\/td><\/tr> <\/table> ","select":[" T\u1ec9 l\u1ec7 thu\u1eadn "," T\u1ec9 l\u1ec7 ngh\u1ecbch "],"hint":"Xem \u0111\u1ecbnh ngh\u0129a t\u1ec9 l\u1ec7 thu\u1eadn, t\u1ec9 l\u1ec7 ngh\u1ecbch. ","explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> * N\u1ebfu \u0111\u1ea1i l\u01b0\u1ee3ng $y$ li\u00ean h\u1ec7 v\u1edbi \u0111\u1ea1i l\u01b0\u1ee3ng $x$ theo c\u00f4ng th\u1ee9c $y = \\dfrac{a}{x} $ hay $xy = a$ (a l\u00e0 m\u1ed9t h\u1eb1ng s\u1ed1 kh\u00e1c 0) th\u00ec ta n\u00f3i $y$ t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi $x$ theo h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 a. <br\/> * N\u1ebfu $y$ li\u00ean h\u1ec7 v\u1edbi $x$ theo c\u00f4ng th\u1ee9c $y = kx (k \\neq 0)$ th\u00ec $y$ t\u1ec9 l\u1ec7 thu\u1eadn v\u1edbi $x$. <\/span> <br\/><br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> Ta c\u00f3: $ \\dfrac{x}{y} = \\dfrac{\\frac{1}{2}}{1\\frac{1}{2}} = \\dfrac{1}{3} = \\dfrac{2}{6} = \\dfrac{4}{12}\\left( = \\dfrac{1}{3}\\right) $ <br\/><br\/><span class='basic_pink'> Suy ra $x$ v\u00e0 $y$ l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 thu\u1eadn. <\/span><\/span> ","column":2}]}],"id_ques":641},{"time":9,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["2"],["18"],["18"]]],"list":[{"point":5,"width":50,"type_input":"","ques":"Cho bi\u1ebft $x$ v\u00e0 $y$ l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch. <br\/> \u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o \u00f4 tr\u1ed1ng.<table> <tr> <td> $x$ <\/td> <td> $x_{1} = 6 $ <\/td> <td> $x_{2} = 9 $ <\/td> <\/tr> <tr> <td> $y$ <\/td> <td> $y_{1} = 3 $ <\/td> <td> $y_{2} = $ _input_ <\/td> <\/tr> <tr> <td> $xy$ <\/td> <td> $x_{1}y_{1} = $ _input_ <\/td> <td> $x_{2}y_{2} = $_input_ <\/td> <\/tr><\/table>","explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> X\u00e1c \u0111\u1ecbnh h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 a, v\u1edbi $a = xy$ <br\/> T\u00ecm $y$ theo c\u00f4ng th\u1ee9c: $ y = \\dfrac{a}{x}. $<\/span> <br\/><br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> V\u00ec $y$ v\u00e0 $x$ l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch n\u00ean $ a = x_{1}y_{1} = x_{2}y_{2}= 6.3 = 18$ <br\/> Suy ra $y$ v\u00e0 $x$ li\u00ean h\u1ec7 v\u1edbi nhau b\u1edfi c\u00f4ng th\u1ee9c: $ y = \\dfrac{18}{x} $ <br\/> V\u1edbi $x_{2} = 9 \\Rightarrow y_{2} = \\dfrac{18}{9} = 2 $<br\/><br\/><span class='basic_pink'> \u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 $ x_{1}y_{1} = 18; y_{2} = 2; x_{2}y_{2} = 18 $. <\/span><\/span> "}]}],"id_ques":642},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":5,"ques":"Ho\u00e0n th\u00e0nh ph\u00e1t bi\u1ec3u sau: <br\/> N\u1ebfu $xy = 24$ v\u00e0 $x$ t\u0103ng g\u1ea5p 3 l\u1ea7n th\u00ec $y$","select":["A. t\u0103ng l\u00ean 3 l\u1ea7n. ","B. gi\u1ea3m \u0111i 3 l\u1ea7n. ","C. t\u0103ng l\u00ean 8 l\u1ea7n. ","D. gi\u1ea3m \u0111i 8 l\u1ea7n."],"explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> N\u1ebfu \u0111\u1ea1i l\u01b0\u1ee3ng $y$ li\u00ean h\u1ec7 v\u1edbi \u0111\u1ea1i l\u01b0\u1ee3ng $x$ theo c\u00f4ng th\u1ee9c $y = \\dfrac{a}{x} $ hay $xy = a$ (a l\u00e0 m\u1ed9t h\u1eb1ng s\u1ed1 kh\u00e1c 0) th\u00ec ta n\u00f3i $y$ t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi $x$ theo h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 a. <\/span> <br\/><br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> Ta c\u00f3 $x$ v\u00e0 $y$ li\u00ean h\u1ec7 v\u1edbi nhau b\u1edfi c\u00f4ng th\u1ee9c $xy = 24$ <br\/> Suy ra $x$ v\u00e0 $y$ l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch. <br\/> V\u1eady khi $x$ t\u0103ng g\u1ea5p 3 l\u1ea7n th\u00ec $y$ gi\u1ea3m \u0111i 3 l\u1ea7n. <br\/><br\/><span class='basic_pink'> \u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 B. <\/span><\/span> ","column":2}]}],"id_ques":643},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"ques":"C\u00f4ng th\u1ee9c n\u00e0o d\u01b0\u1edbi \u0111\u00e2y kh\u00f4ng cho ta quan h\u1ec7 t\u1ec9 l\u1ec7 ngh\u1ecbch?","select":["A. $2y = \\dfrac{1}{x} $","B. $xy = 2$","C. $y = 3x$ ","D. $3 = \\dfrac{1}{xy} $"],"explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> N\u1ebfu \u0111\u1ea1i l\u01b0\u1ee3ng $y$ li\u00ean h\u1ec7 v\u1edbi \u0111\u1ea1i l\u01b0\u1ee3ng $x$ theo c\u00f4ng th\u1ee9c $y = \\dfrac{a}{x} $ hay $xy = a$ (a l\u00e0 m\u1ed9t h\u1eb1ng s\u1ed1 kh\u00e1c 0) th\u00ec ta n\u00f3i $y$ t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi $x$ theo h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 a. <\/span> <br\/><br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> C\u00f4ng th\u1ee9c kh\u00f4ng cho ta quan h\u1ec7 t\u1ec9 l\u1ec7 ngh\u1ecbch l\u00e0 <br\/> $y = 3x$ (\u0111\u00e2y l\u00e0 quan h\u1ec7 t\u1ec9 l\u1ec7 thu\u1eadn) <br\/><br\/><span class='basic_pink'> Ch\u1ecdn \u0111\u00e1p \u00e1n C. <\/span><\/span> ","column":2}]}],"id_ques":644},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"ques":"Hai \u0111\u1ea1i l\u01b0\u1ee3ng n\u00e0o d\u01b0\u1edbi \u0111\u00e2y c\u00f3 m\u1ed1i li\u00ean h\u1ec7 t\u1ec9 l\u1ec7 ngh\u1ecbch?","select":["A. Di\u1ec7n t\u00edch S c\u1ee7a h\u00ecnh vu\u00f4ng v\u00e0 \u0111\u1ed9 d\u00e0i a (m\u00e9t) c\u1ea1nh c\u1ee7a h\u00ecnh vu\u00f4ng \u0111\u00f3. ","B. Dung t\u00edch c\u1ee7a m\u1ed9t b\u1ec3 ch\u1ee9a c (l\u00edt) v\u00e0 chi\u1ec1u cao h (m\u00e9t) c\u1ee7a b\u1ec3 ch\u1ee9a \u0111\u00f3.","C. V\u1eadn t\u1ed1c v (km\/h) v\u00e0 th\u1eddi gian t (gi\u1edd) c\u1ea7n ph\u1ea3i c\u00f3 \u0111\u1ec3 m\u1ed9t \u0111o\u00e0n t\u00e0u \u0111i t\u1eeb A \u0111\u1ebfn B. ","D. Tr\u1ecb gi\u00e1 ti\u1ec1n l\u00e3i ti\u1ebft ki\u1ec7m R (\u0111\u1ed3ng) theo th\u1eddi h\u1ea1n T (tu\u1ea7n l\u1ec5)."],"explain":" Ta c\u00f3: Tr\u00ean c\u00f9ng m\u1ed9t qu\u00e3ng \u0111\u01b0\u1eddng th\u00ec th\u1eddi gian v\u00e0 v\u1eadn t\u1ed1c l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch. <br\/><br\/><span class='basic_pink'> \u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 C. <\/span><\/span> ","column":1}]}],"id_ques":645},{"time":9,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["108"],["27"],["3"]]],"list":[{"point":5,"width":50,"type_input":"","ques":"Gi\u1ea3 s\u1eed $y = \\dfrac{a}{x} $ v\u00e0 khi $y = 12$ th\u00ec $x = 9$. <br\/> Gi\u00e1 tr\u1ecb $a = \\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}$ <br\/> Khi $x = 4$ th\u00ec $ y = \\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}$ <br\/> Khi $y = 36$ th\u00ec $x = \\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}$","hint":"X\u00e1c \u0111\u1ecbnh h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 $a = xy$, sau \u0111\u00f3 thay v\u00e0o r\u1ed3i t\u00ecm $x, y$.","explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> X\u00e1c \u0111\u1ecbnh h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 a, v\u1edbi $a = xy$ <br\/> T\u00ecm $y$ theo c\u00f4ng th\u1ee9c: $ y = \\dfrac{a}{x} $ <br\/> T\u00ecm $x$ theo c\u00f4ng th\u1ee9c: $ x = \\dfrac{a}{y} $<\/span> <br\/><br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> V\u00ec $y$ v\u00e0 $x$ li\u00ean h\u1ec7 v\u1edbi nhau b\u1edfi c\u00f4ng th\u1ee9c $y = \\dfrac{a}{x} $ n\u00ean $y$ v\u00e0 $x$ l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch .<br\/> H\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 $ a = xy =12.9 = 108$ <br\/> Khi $x = 4$ th\u00ec $ y = \\dfrac{a}{x} = \\dfrac{108}{4} = 27$ <br\/> Khi $y = 36$ th\u00ec $ x = \\dfrac{a}{y} = \\dfrac{108}{36} = 3 $ <br\/><br\/><span class='basic_pink'> \u0110\u00e1p s\u1ed1 l\u00e0 108, 27, 3. <\/span><\/span> "}]}],"id_ques":646},{"time":9,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["6"],["32"]]],"list":[{"point":5,"width":50,"type_input":"","ques":"Cho bi\u1ebft $x$ v\u00e0 $y$ l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch. <br\/> \u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o \u00f4 tr\u1ed1ng. <table> <tr> <td> $x$ <\/td> <td> 3 <\/td> <td> _input_ <\/td> <td> 12 <\/td> <\/tr> <tr> <td> $y$ <\/td> <td> _input_ <\/td> <td> 16 <\/td> <td> 8 <\/td> <\/tr> <\/table>","hint":"X\u00e1c \u0111\u1ecbnh h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 $a = xy$, sau \u0111\u00f3 thay v\u00e0o r\u1ed3i t\u00ecm $x, y$.","explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> X\u00e1c \u0111\u1ecbnh h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 a, v\u1edbi $a = xy$ <br\/> T\u00ecm $y$ theo c\u00f4ng th\u1ee9c: $ y = \\dfrac{a}{x} $ <br\/> T\u00ecm $x$ theo c\u00f4ng th\u1ee9c: $ x = \\dfrac{a}{y} $<\/span> <br\/><br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> V\u00ec $y$ v\u00e0 $x$ l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch n\u00ean t\u1eeb c\u1ed9t cu\u1ed1i ta t\u00ednh \u0111\u01b0\u1ee3c: <br\/> $ a = xy =12.8 = 96$ <br\/> T\u1eeb \u0111\u00f3 t\u00ednh \u0111\u01b0\u1ee3c c\u00e1c s\u1ed1 c\u00f2n l\u1ea1i. K\u1ebft qu\u1ea3 xem b\u1ea3ng sau : <table> <tr> <td> $x$ <\/td> <td> 3 <\/td> <td> <b><span class='basic_pink'>6<\/span><\/b> <\/td> <td> 12 <\/td> <\/tr> <tr> <td> $y$ <\/td> <td> <b> <span class='basic_pink'>32<\/span> <\/b><\/td> <td> 16 <\/td> <td> 8 <\/td> <\/tr> <\/table> <\/span><\/span> "}]}],"id_ques":647},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":5,"ques":"<span class='basic_left'> Cho $x$ v\u00e0 $y$ l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch v\u00e0 khi $x = \\dfrac{-3}{2} $ th\u00ec $y = \\dfrac{2}{3}$. T\u00ednh gi\u00e1 tr\u1ecb c\u1ee7a $y$ khi $x$ b\u1eb1ng 1? <\/span>","select":["A. $1$ ","B. $-1$","C. $\\dfrac{-9}{4} $","D. $\\dfrac{4}{9} $ "],"hint":"+ T\u00ecm h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 $a$. <br\/> + Thay v\u00e0o c\u00f4ng th\u1ee9c r\u1ed3i t\u00ecm $y$.","explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> B\u01b0\u1edbc 1: X\u00e1c \u0111\u1ecbnh h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 $a$, v\u1edbi $a = xy$ <br\/> B\u01b0\u1edbc 2: T\u00ecm $y$ theo c\u00f4ng th\u1ee9c: $y = \\dfrac{a}{x}.$ <\/span> <br\/><br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> V\u00ec $x$ v\u00e0 $y$ l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch n\u00ean: <br\/> $a = xy = \\dfrac{-3}{2}.\\dfrac{2}{3} = -1 $ <br\/> Do \u0111\u00f3 $y$ v\u00e0 $x$ li\u00ean h\u1ec7 v\u1edbi nhau b\u1edfi c\u00f4ng th\u1ee9c: $ y = \\dfrac{-1}{x}$. <br\/> V\u1eady khi $x = 1$ th\u00ec $ y = \\dfrac{-1}{1} = -1 $ <br\/><br\/><span class='basic_pink'> \u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 B. <\/span><\/span> ","column":4}]}],"id_ques":648},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":5,"ques":"<span class='basic_left'> Cho $x$ v\u00e0 $y$ l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch v\u00e0 khi $x$ = 1,2 th\u00ec $y$ = 5. C\u00f4ng th\u1ee9c li\u00ean h\u1ec7 gi\u1eefa $y$ v\u00e0 $x$ l\u00e0: <\/span>","select":["A. $ y = \\dfrac{25}{6}x$ ","B. $y = \\dfrac{6}{x}$ ","C. $y = 6x$ ","D. $ y = \\dfrac{6}{25} x$ "],"explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> B1. X\u00e1c \u0111\u1ecbnh h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 $a$, v\u1edbi $a = xy$ <br\/> B2. Bi\u1ec3u di\u1ec5n $y$ theo $x$ b\u1edfi c\u00f4ng th\u1ee9c: $y = \\dfrac{a}{x}.$ <\/span> <br\/><br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> V\u00ec $x$ v\u00e0 $y$ l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch n\u00ean: <br\/> $a = xy = 1,2.5 = 6 $ <br\/> Suy ra $y$ v\u00e0 $x$ li\u00ean h\u1ec7 v\u1edbi nhau b\u1edfi c\u00f4ng th\u1ee9c: $ y = \\dfrac{6}{x}$. <br\/><br\/><span class='basic_pink'> \u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 B. <\/span><\/span> ","column":2}]}],"id_ques":649},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[4]],"list":[{"point":5,"ques":"<span class='basic_left'> Cho $x$ v\u00e0 $y$ l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch v\u00e0 khi $x$ = 3 th\u00ec $y$ = 4,5. H\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 $a$ c\u1ee7a $y$ \u0111\u1ed1i v\u1edbi $x$ l\u00e0: <\/span>","select":["A. $\\dfrac{3}{2}$ ","B. $\\dfrac{2}{3}$","C. $7,5$ ","D. $13,5$ "],"explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> X\u00e1c \u0111\u1ecbnh h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 $a$, v\u1edbi $a = xy$ <\/span> <br\/><br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> V\u00ec $x$ v\u00e0 $y$ l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch n\u00ean: <br\/> $a = xy = 3.4,5 = 13,5 $ <br\/> V\u1eady h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 $a = 13,5$ <br\/><br\/><span class='basic_pink'> \u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 D. <\/span><\/span> ","column":2}]}],"id_ques":650}],"lesson":{"save":0,"level":2}}