{"common":{"save":0,"post_id":"977","level":3,"total":10,"point":10,"point_extra":0},"segment":[{"id":"291","post_id":"977","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":" Cho t\u1ec9 l\u1ec7 th\u1ee9c $ \\dfrac{5x - 2y}{3x + 4y} = \\dfrac{3}{4} $ (v\u1edbi $3x + 4y \\neq 0$). T\u00ednh gi\u00e1 tr\u1ecb c\u1ee7a t\u1ec9 s\u1ed1 $\\dfrac{x}{y} (y \\neq 0)$ ","select":["A. $\\dfrac{x}{y} = \\dfrac{11}{20}$ ","B. $\\dfrac{x}{y} = \\dfrac{20}{11}$ ","C. $\\dfrac{x}{y} = \\dfrac{3}{4}$ ","D. $\\dfrac{x}{y} = \\dfrac{4}{3}$ "],"hint":"\u00c1p d\u1ee5ng: $\\dfrac{a}{b} = \\dfrac{c}{d} \\Rightarrow ad = bc $ ","explain":" Theo t\u00ednh ch\u1ea5t c\u1ee7a t\u1ec9 l\u1ec7 th\u1ee9c ta c\u00f3: <br\/> $ \\dfrac{5x - 2y}{3x + 4y} = \\dfrac{3}{4} \\\\ \\Rightarrow 4(5x - 2y) = 3(3x + 4y) \\\\ \\Rightarrow 20x - 8y = 9x + 12y \\\\ \\Rightarrow 20x - 9x = 8y + 12y \\\\ \\Rightarrow 11x = 20y \\\\ \\Rightarrow \\dfrac{x}{y} = \\dfrac{20}{11} (y \\neq 0) $ <br\/> V\u1eady $\\dfrac{x}{y} = \\dfrac{20}{11}$ <br\/> <br\/> <span class='basic_pink'> \u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 B. <\/span><\/span> ","column":2}]}]},"correct":"","level":"3","hint":"","answer":"","type":"json","extra_type":"","time":"0","user_id":"0","test":"0","date":"2019-09-30 09:22:45"},{"id":"292","post_id":"977","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":10,"ques":" T\u00ecm $x $ trong t\u1ec9 l\u1ec7 th\u1ee9c sau: $ \\dfrac{3x+2}{5x+7} = \\dfrac{3x-1}{5x+1} $ ","select":["A. $ x = 3 $ ","B. $ x = -3 $ ","C. $ x = -5 $ ","D. $ x = 5 $ "],"hint":" $ \\dfrac{a}{b} = \\dfrac{c}{d} \\Rightarrow ad = bc$ ","explain":" <span class='basic_left'> \u00c1p d\u1ee5ng t\u00ednh ch\u1ea5t c\u1ee7a t\u1ec9 l\u1ec7 th\u1ee9c ta c\u00f3: <br\/> $ \\dfrac{3x+2}{5x+7} = \\dfrac{3x-1}{5x+1} \\\\ \\Rightarrow (3x + 2)(5x + 1) = (5x + 7)(3x - 1) \\\\ \\Rightarrow 3x(5x + 1) + 2(5x + 1) = 5x(3x - 1) + 7(3x - 1) \\\\ \\Rightarrow 15x^{2} + 3x + 10x + 2 = 15x^{2} - 5x + 21x - 7 \\\\ \\Rightarrow 13x + 2 = 16x - 7 \\\\ \\Rightarrow 13x - 16x = -2 - 7 \\\\ \\Rightarrow -3x = -9 \\\\ \\Rightarrow x = 3 $ <br\/> V\u1eady gi\u00e1 tr\u1ecb c\u1ee7a x l\u00e0 $ 3 $ <br\/> <br\/> <span class='basic_pink'> \u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 A. <\/span><\/span>","column":2}]}]},"correct":"","level":"3","hint":"","answer":"","type":"json","extra_type":"","time":"0","user_id":"0","test":"0","date":"2019-09-30 09:22:45"},{"id":"293","post_id":"977","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":[[["70"],["40"]]],"list":[{"point":10,"width":50,"type_input":"","ques":" T\u00ecm $x, y$ bi\u1ebft: $\\dfrac{x}{7} = \\dfrac{y}{4}$ v\u00e0 $x - y = 30$ <br\/> <b> \u0110\u00e1p s\u1ed1: <\/b> $x $= _input_; $y$ = _input_","hint":" \u0110\u1eb7t \u1ea9n ph\u1ee5: $\\dfrac{x}{7} = \\dfrac{y}{4} = k $ v\u00e0 bi\u1ec3u di\u1ec5n x, y theo k r\u1ed3i th\u1ebf v\u00e0o gi\u1ea3 thi\u1ebft th\u1ee9 2 ","explain":" Ta c\u00f3: $\\dfrac{x}{7} = \\dfrac{y}{4}$ (1) v\u00e0 $x - y = 30$ (2) <br\/> T\u1eeb (1): \u0110\u1eb7t $\\dfrac{x}{7} = \\dfrac{y}{4} = k \\Rightarrow \\begin{cases} x = 7k \\\\ y = 4k \\end{cases} $ <br\/> Thay $x = 7k; y = 4k$ v\u00e0o (2) ta \u0111\u01b0\u1ee3c: <br\/> $7k - 4k = 30 \\Rightarrow 3k = 30 \\Rightarrow k = 10 $ <br\/> Suy ra $\\begin{cases} x = 7.10 = 70 \\\\ y = 4.10 = 40 \\end{cases} $ <br\/> <br\/> <span class='basic_pink'> V\u1eady gi\u00e1 tr\u1ecb c\u1ee7a $x, y$ l\u00e0 $ \\begin{cases} x = 70 \\\\ y = 40 \\end{cases} $ <\/span><\/span>"}]}]},"correct":"","level":"3","hint":"","answer":"","type":"json","extra_type":"","time":"0","user_id":"0","test":"0","date":"2019-09-30 09:22:45"}]}