{"common":{"save":0,"post_id":"982","level":2,"total":20,"point":5,"point_extra":0},"segment":[{"id":"321","post_id":"982","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":[[1]],"list":[{"point":5,"ques":" T\u00ecm $x, y$ bi\u1ebft:<br\/> $5x = 2y$ v\u00e0 $3x + 7y = - 82$ ","select":["A.$x = -4; y = -10$ ","B. $ x = -4; y = -8$ ","C. $x = 4; y = 10$","D. $x = -8; y = -20$"],"hint":" Ta c\u00f3: $5x = 2y \\Rightarrow \\dfrac{x}{2} = \\dfrac{y}{5} = \\dfrac{3x+7y}{3.2+7.5}$","explain":" Ta c\u00f3: $5x = 2y \\Rightarrow \\dfrac{x}{2} = \\dfrac{y}{5}$ <br\/> \u00c1p d\u1ee5ng t\u00ednh ch\u1ea5t d\u00e3y t\u1ec9 s\u1ed1 b\u1eb1ng nhau, ta \u0111\u01b0\u1ee3c: <br\/> $ \\dfrac{x}{2} = \\dfrac{y}{5} = \\dfrac{3x+7y}{3.2+7.5} = \\dfrac{-82}{41} = -2$ <br\/> Suy ra: $ \\dfrac{x}{2} = -2 \\Rightarrow x = -4 \\\\ \\dfrac{y}{5} = -2 \\Rightarrow y = -10 $ <br\/> <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 A. <\/span><\/span> ","column":2}]}]},"correct":"","level":"2","hint":"","answer":"","type":"json","extra_type":"","time":"0","user_id":"0","test":"0","date":"2019-09-30 09:22:45"},{"id":"322","post_id":"982","mon_id":"0","chapter_id":"0","question":"\u0110i\u1ec1n \u0111\u00e1p \u00e1n \u0111\u00fang v\u00e0o \u00f4 tr\u1ed1ng","options":{"time":24,"part":[{"title":"\u0110i\u1ec1n \u0111\u00e1p \u00e1n \u0111\u00fang v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["6"],["4"],["8"]]],"list":[{"point":5,"width":50,"type_input":"","ques":" T\u00ecm $x, y$ bi\u1ebft:<br\/> $\\dfrac{x}{3} = \\dfrac{y}{2} = \\dfrac{z}{4}$ v\u00e0 $x.y.z = 192$ <br\/> <br\/> <b> \u0110\u00e1p s\u1ed1: <\/b> $x = $ _input_;$y =$ _input_","hint":" \u0110\u1eb7t : $\\dfrac{x}{3} = \\dfrac{y}{2} = \\dfrac{z}{4} = k $ r\u1ed3i bi\u1ec3u di\u1ec5n x, y, z theo k v\u00e0 th\u1ebf v\u00e0o gi\u1ea3 thi\u1ebft c\u00f2n l\u1ea1i","explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> <b> D\u1ea1ng to\u00e1n: T\u00ecm c\u00e1c s\u1ed1 h\u1ea1ng trong m\u1ed9t d\u00e3y t\u1ec9 s\u1ed1 b\u1eb1ng nhau bi\u1ebft t\u00edch c\u1ee7a c\u00e1c s\u1ed1 h\u1ea1ng \u0111\u00f3 <\/b> <br\/> <i><u> Ph\u01b0\u01a1ng ph\u00e1p gi\u1ea3i <\/i> <\/u> <br\/> N\u1ebfu $\\dfrac{x}{a} = \\dfrac{y}{b} = \\dfrac{z}{c}$ v\u00e0 $x. y . z = p$ <br\/> Th\u00ec ta \u0111\u1eb7t $ \\dfrac{x}{a} = \\dfrac{y}{b} = \\dfrac{z}{c} = k $ suy ra $\\begin{cases} x = ak \\\\ y = bk \\\\ z = ck \\end{cases} $ <br\/> T\u00ecm $k$ r\u1ed3i suy ra $x, y, z$. <\/span> <br\/><br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> \u0110\u1eb7t $\\dfrac{x}{3} = \\dfrac{y}{2} = \\dfrac{z}{4} = k \\\\ \\Rightarrow \\begin{cases} x = 3k \\\\ y = 2k \\\\ z = 4k \\end{cases} $ <br\/> Do \u0111\u00f3: $x.y.z = (3k).(2k).(4k) = 24k^{3}$ <br\/> Suy ra $24k^{3} = 192 \\Rightarrow k^{3} = \\dfrac{192}{24} = 8 \\Rightarrow k = 2 $ <br\/> Suy ra $\\dfrac{x}{3} = 2 \\Rightarrow x = 3.2 = 6 \\\\ \\dfrac{y}{2} = 2 \\Rightarrow y = 2.2 = 4 \\\\ \\dfrac{z}{4} = 2 \\Rightarrow z = 2.4 = 8 $ <br\/> <span class='basic_pink'> V\u1eady c\u00e1c gi\u00e1 tr\u1ecb c\u1ea7n \u0111i\u1ec1n l\u1ea7n l\u01b0\u1ee3t l\u00e0 $6; 8; 4$ <\/span><\/span>"}]}]},"correct":"","level":"2","hint":"","answer":"","type":"json","extra_type":"","time":"0","user_id":"0","test":"0","date":"2019-09-30 09:22:45"},{"id":"323","post_id":"982","mon_id":"0","chapter_id":"0","question":"\u0110i\u1ec1n \u0111\u00e1p \u00e1n \u0111\u00fang v\u00e0o \u00f4 tr\u1ed1ng","options":{"time":24,"part":[{"title":"\u0110i\u1ec1n \u0111\u00e1p \u00e1n \u0111\u00fang v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["18"],["27"],["54"]]],"list":[{"point":5,"width":50,"type_input":"","ques":"T\u00ecm $x, y, z$ bi\u1ebft: <br\/> $ 3x = 2y = z $ v\u00e0 $x + y + z = 99 ?$ <br\/><br\/> <b> \u0110\u00e1p s\u1ed1: <\/b>$x = $ _input_;$y =$ _input_; $z=$_input_","hint":" T\u1eeb: $3x = 2y = z $ ta chia cho BCNN(3; 2; 1) l\u00e0m xu\u1ea5t hi\u1ec7n d\u00e3y t\u1ec9 s\u1ed1 b\u1eb1ng nhau","explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> T\u00ednh ch\u1ea5t m\u1edf r\u1ed9ng c\u1ee7a d\u00e3y t\u1ec9 s\u1ed1 b\u1eb1ng nhau <\/b> <\/br> N\u1ebfu $\\dfrac{x}{a} = \\dfrac{y}{b} = \\dfrac{z}{c}$ th\u00ec <br\/> $\\dfrac{x}{a} = \\dfrac{y}{b} = \\dfrac{z}{c} = \\dfrac{xm-yn+zt}{am-bn+ct}$<\/span> <br\/><br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/> T\u1eeb: $3x = 2y = z $ ta chia cho BCNN(3; 2; 1) = 6, ta \u0111\u01b0\u1ee3c: <br\/> $ \\dfrac{x}{2} = \\dfrac{y}{3} = \\dfrac{z}{6} $ <br\/> \u00c1p d\u1ee5ng t\u00ednh ch\u1ea5t d\u00e3y t\u1ec9 s\u1ed1 b\u1eb1ng nhau ta c\u00f3: <br\/> $\\dfrac{x}{2} = \\dfrac{y}{3} = \\dfrac{z}{6} = \\dfrac{x+y+z}{2+3+6} = \\dfrac{99}{11} = 9 $ <br\/> Suy ra $ \\dfrac{x}{2} = 9 \\Rightarrow x = 2.9 = 18 \\\\ \\dfrac{y}{3} = 9 \\Rightarrow y = 3.9 = 27 \\\\ \\dfrac{z}{6} = 9 \\Rightarrow z = 6.9 = 54 $ <br\/> <br\/> <span class='basic_pink'> V\u1eady c\u00e1c gi\u00e1 tr\u1ecb c\u1ea7n \u0111i\u1ec1n l\u1ea7n l\u01b0\u1ee3t l\u00e0 $18; 27; 54$ <\/span><\/span>"}]}]},"correct":"","level":"2","hint":"","answer":"","type":"json","extra_type":"","time":"0","user_id":"0","test":"0","date":"2019-09-30 09:22:45"}]}