{"common":{"save":0,"post_id":"986","level":3,"total":10,"point":10,"point_extra":0},"segment":[{"id":"851","post_id":"986","mon_id":"0","chapter_id":"0","question":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","options":{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[4]],"list":[{"point":10,"ques":"Cho bi\u1ebft \u0111\u1ea1i l\u01b0\u1ee3ng $x$ t\u1ec9 l\u1ec7 thu\u1eadn v\u1edbi \u0111\u1ea1i l\u01b0\u1ee3ng $y$ theo h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 $k$. \u0110\u1ea1i l\u01b0\u1ee3ng $y$ t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi \u0111\u1ea1i l\u01b0\u1ee3ng $z$ theo h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 $k$. Khi \u0111\u00f3: ","select":["A. \u0110\u1ea1i l\u01b0\u1ee3ng $y$ t\u1ec9 l\u1ec7 thu\u1eadn v\u1edbi \u0111\u1ea1i l\u01b0\u1ee3ng $x$ theo h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 $k$. ","B. \u0110\u1ea1i l\u01b0\u1ee3ng $x$ t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi \u0111\u1ea1i l\u01b0\u1ee3ng $z$ theo h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 $k$. ","C. \u0110\u1ea1i l\u01b0\u1ee3ng $x$ t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi \u0111\u1ea1i l\u01b0\u1ee3ng $z$ theo h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 $2k$. ","D. \u0110\u1ea1i l\u01b0\u1ee3ng $x$ t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi \u0111\u1ea1i l\u01b0\u1ee3ng $z$ theo h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 $k^{2} $. "],"explain":"<span class='basic_left'> \u0110\u1ea1i l\u01b0\u1ee3ng $x$ t\u1ec9 l\u1ec7 thu\u1eadn v\u1edbi \u0111\u1ea1i l\u01b0\u1ee3ng $y$ theo h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 $k$ th\u00ec \u0111\u1ea1i l\u01b0\u1ee3ng $y$ t\u1ec9 l\u1ec7 thu\u1eadn v\u1edbi \u0111\u1ea1i l\u01b0\u1ee3ng $x$ theo h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 $\\dfrac{1}{k} \\Rightarrow A $ Sai. <br\/> Ta c\u00f3: \u0111\u1ea1i l\u01b0\u1ee3ng $x$ t\u1ec9 l\u1ec7 thu\u1eadn v\u1edbi \u0111\u1ea1i l\u01b0\u1ee3ng $y$ theo h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 $k$ n\u00ean $x = ky (1)$ <br\/> \u0110\u1ea1i l\u01b0\u1ee3ng $y$ t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi \u0111\u1ea1i l\u01b0\u1ee3ng $z$ theo h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 $k$ n\u00ean $y = \\dfrac{k}{z} \\Rightarrow z = \\dfrac{k}{y} (2) $ <br\/> T\u1eeb (1) v\u00e0 (2) ta c\u00f3: $x.z = ky. \\dfrac{k}{y} = k^{2} $ <br\/> Do \u0111\u00f3 \u0111\u1ea1i l\u01b0\u1ee3ng $x$ t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi \u0111\u1ea1i l\u01b0\u1ee3ng $z$ theo h\u1ec7 s\u1ed1 t\u1ec9 l\u1ec7 $k^{2} $ <br\/> V\u1eady \u0111\u00e1p \u00e1n D \u0111\u00fang; \u0111\u00e1p \u00e1n B, C Sai. <br\/><br\/> <span class='basic_pink'>\u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 D. <\/span>","column":1}]}]},"correct":"","level":"3","hint":"","answer":"","type":"json","extra_type":"","time":"0","user_id":"0","test":"0","date":"2019-09-30 09:22:52"},{"id":"852","post_id":"986","mon_id":"0","chapter_id":"0","question":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","options":{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":10,"ques":"<span class='basic_left'>M\u1ed9t \u00f4 t\u00f4 \u0111i t\u1eeb A \u0111\u1ebfn B v\u1edbi v\u1eadn t\u1ed1c 48 km\/h. L\u00fac v\u1ec1 xe \u0111i qu\u00e3ng \u0111\u01b0\u1eddng BA v\u1edbi v\u1eadn t\u1ed1c 42 km\/h. Bi\u1ebft th\u1eddi gian c\u1ea3 \u0111i l\u1eabn v\u1ec1 l\u00e0 7 gi\u1edd 30 ph\u00fat. T\u00ednh \u0111\u1ed9 d\u00e0i qu\u00e3ng \u0111\u01b0\u1eddng AB. <\/span> ","select":["A. 192 km ","B. 168 km ","C. 336 km ","D. 360 km "],"explain":"<span class='basic_left'> \u0110\u1ed5i: 7 gi\u1edd 30 ph\u00fat = 7,5 gi\u1edd. <br\/> G\u1ecdi th\u1eddi gian l\u00fac xe \u0111i t\u1eeb A \u0111\u1ebfn B v\u00e0 t\u1eeb B v\u1ec1 A l\u1ea7n l\u01b0\u1ee3t l\u00e0 $t_{1}, t_{2} $ (gi\u1edd, $t_{1}, t_{2} > 0$ ) <br\/> V\u1eadn t\u1ed1c l\u00fac xe \u0111i t\u1eeb A \u0111\u1ebfn B v\u00e0 t\u1eeb B v\u1ec1 A l\u1ea7n l\u01b0\u1ee3t l\u00e0 $v_{1}, v_{2} $ <br\/> Theo b\u00e0i c\u00f3: $t_{1} + t_{2} = 7, 5 \\\\ v_{1} = 48 , v_{2} = 42 $ <br\/> V\u00ec th\u1eddi gian v\u00e0 v\u1eadn t\u1ed1c \u0111i c\u00f9ng m\u1ed9t qu\u00e3ng \u0111\u01b0\u1eddng l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch, n\u00ean ta c\u00f3: <br\/> $\\begin{aligned}& \\dfrac{{{t}_{1}}}{{{t}_{2}}}=\\dfrac{{{v}_{2}}}{{{v}_{1}}}=\\dfrac{42}{48}=\\dfrac{7}{8} \\\\ & \\Rightarrow \\dfrac{{{t}_{1}}}{7}=\\dfrac{{{t}_{2}}}{8}=\\dfrac{{{t}_{1}}+{{t}_{2}}}{7+8}=\\dfrac{7,5}{15}=0,5 \\\\ & \\Rightarrow \\left\\{\\begin{aligned} & {{t}_{1}}=7.0,5=3,5 \\\\ & {{t}_{2}}=8.0,5=4 \\\\ \\end{aligned} \\right. \\\\ \\end{aligned}$ <br\/> \u0110\u1ed9 d\u00e0i qu\u00e3ng \u0111\u01b0\u1eddng AB l\u00e0: $t_{1}.v_{1} = 3,5.48 = 168 (km) $ <br\/><br\/> <span class='basic_pink'>\u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 B. <\/span>","column":2}]}]},"correct":"","level":"3","hint":"","answer":"","type":"json","extra_type":"","time":"0","user_id":"0","test":"0","date":"2019-09-30 09:22:52"},{"id":"853","post_id":"986","mon_id":"0","chapter_id":"0","question":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","options":{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[4]],"list":[{"point":10,"ques":"<span class='basic_left'>Hai xe m\u00e1y c\u00f9ng \u0111i t\u1eeb A \u0111\u1ebfn B. Xe th\u1ee9 I \u0111i h\u1ebft 1 gi\u1edd 20 ph\u00fat, xe th\u1ee9 II \u0111i h\u1ebft 1 gi\u1edd 30 ph\u00fat. T\u00ecm v\u1eadn t\u1ed1c trung b\u00ecnh m\u1ed7i xe. Bi\u1ebft r\u1eb1ng trung b\u00ecnh m\u1ed7i ph\u00fat xe th\u1ee9 I \u0111i nhanh h\u01a1n xe th\u1ee9 II l\u00e0 100m. <\/span> ","select":["A. 990, 880 (m\/ph\u00fat) ","B. 950, 850 (m\/ph\u00fat) ","C. 700, 900 (m\/ph\u00fat) ","D. 900, 800 (m\/ph\u00fat) "],"explain":"<span class='basic_left'>\u0110\u1ed5i: 1 gi\u1edd 20 ph\u00fat = 80 ph\u00fat; 1 gi\u1edd 30 ph\u00fat = 90 ph\u00fat <br\/> G\u1ecdi $v_{1}, v_{2} $ l\u1ea7n l\u01b0\u1ee3t l\u00e0 v\u1eadn t\u1ed1c c\u1ee7a xe th\u1ee9 I v\u00e0 xe th\u1ee9 II.<br\/> Theo \u0111\u1ea7u b\u00e0i ta c\u00f3: $v_{1} - v_{2} = 100 $ <br\/> Tr\u00ean c\u00f9ng qu\u00e3ng \u0111\u01b0\u1eddng AB th\u00ec v\u1eadn t\u1ed1c v\u00e0 th\u1eddi gian l\u00e0 hai \u0111\u1ea1i l\u01b0\u1ee3ng t\u1ec9 l\u1ec7 ngh\u1ecbch n\u00ean ta c\u00f3: $\\dfrac{{{v}_{1}}}{{{v}_{2}}}=\\dfrac{90}{80}$ <br\/> Do \u0111\u00f3: $\\begin{aligned}& \\frac{{{v}_{1}}}{90}=\\frac{{{v}_{2}}}{80}=\\dfrac{{{v}_{1}}-{{v}_{2}}}{90-80}=\\dfrac{100}{10}=10 \\\\& \\Rightarrow \\left\\{ \\begin{aligned}& {{v}_{1}}=90.10=900 \\\\ & {{v}_{2}}=80.10=800 \\\\ \\end{aligned} \\right. \\\\ \\end{aligned}$ <br\/> V\u1eadn t\u1ed1c trung b\u00ecnh xe th\u1ee9 I, II l\u1ea7n l\u01b0\u1ee3t l\u00e0: 900, 800 (m\/ph\u00fat) <br\/><br\/> <span class='basic_pink'>\u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 D. <\/span>","column":2}]}]},"correct":"","level":"3","hint":"","answer":"","type":"json","extra_type":"","time":"0","user_id":"0","test":"0","date":"2019-09-30 09:22:52"}]}