{"common":{"save":0,"post_id":"979","level":1,"total":20,"point":5,"point_extra":0},"segment":[{"id":"301","post_id":"979","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":5,"ques":" T\u00ecm $x, y, z$ bi\u1ebft: <br\/> $\\dfrac{x}{9} = \\dfrac{y}{5} = \\dfrac{z}{10}$ v\u00e0 $x - y + z = 70$ ","select":["A. $x = 9; y = 5; z = 10 $ ","B. $x = 27; y = 15; z = 30 $ ","C. $x = 36; y = 20; z = 40 $ ","D. $x = 45; y = 25; z = 50 $ "],"hint":" \u00c1p d\u1ee5ng t\u00ednh ch\u1ea5t c\u1ee7a 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\/> <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\u1ed5ng,hi\u1ec7u c\u1ee7a c\u00e1c s\u1ed1 h\u1ea1ng \u0111\u00f3<\/b> <br\/> <i> Ph\u01b0\u01a1ng ph\u00e1p gi\u1ea3i <\/i> <br\/> N\u1ebfu $\\dfrac{x}{a} = \\dfrac{y}{b} = \\dfrac{z}{c}$ v\u00e0 $x - y + z = M$ <br\/> Th\u00ec $\\dfrac{x}{a} = \\dfrac{y}{b} = \\dfrac{z}{c} = \\dfrac{x-y+z}{a-b+c} = \\dfrac{M}{a-b+c}$ <br\/> T\u1eeb \u0111\u00f3 t\u00ecm \u0111\u01b0\u1ee3c $x, y, z$. <\/span> <br\/> <br\/> <span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/>Theo t\u00ednh ch\u1ea5t c\u1ee7a d\u00e3y t\u1ec9 s\u1ed1 b\u1eb1ng nhau, ta c\u00f3: <br\/> $\\dfrac{x}{9} = \\dfrac{y}{5} = \\dfrac{z}{10} = \\dfrac{x-y+z}{9-5+10} = \\dfrac{70}{14} = 5 $ <br\/> Suy ra: $\\dfrac{x}{9} = 5 \\Rightarrow x = 9.5 = 45 \\\\ \\dfrac{y}{5} = 5 \\Rightarrow y = 5.5 = 25 \\\\ \\dfrac{z}{10} = 5 \\Rightarrow z = 10.5 = 50$ <br\/> V\u1eady gi\u00e1 tr\u1ecb c\u1ee7a $x, y, z$ l\u00e0: $\\begin{cases} x = 45 \\\\ y = 25 \\\\ z = 50 \\end{cases}$ <br\/> <br\/> <span class='basic_pink'> \u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 D. <\/span><\/span> ","column":2}]}]},"correct":"","level":"1","hint":"","answer":"","type":"json","extra_type":"","time":"0","user_id":"0","test":"0","date":"2019-09-30 09:22:45"},{"id":"302","post_id":"979","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":5,"ques":" T\u00ecm $x, y, z$ bi\u1ebft: <br\/> $\\dfrac{x}{8} = \\dfrac{y}{5} = \\dfrac{z}{12}$ v\u00e0 $x + y + z = -100 $ ","select":["A. $x = 32; y = 20; z = 48 $ ","B. $x = -32; y = -20; z = -48 $ ","C. $x = -32; y = -20; z = 48 $ "],"hint":" \u00c1p d\u1ee5ng t\u00ednh ch\u1ea5t c\u1ee7a 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\/> <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\u1ed5ng,hi\u1ec7u c\u1ee7a c\u00e1c s\u1ed1 h\u1ea1ng \u0111\u00f3<\/b> <br\/> <i> Ph\u01b0\u01a1ng ph\u00e1p gi\u1ea3i <\/i> <br\/> N\u1ebfu $\\dfrac{x}{a} = \\dfrac{y}{b} = \\dfrac{z}{c}$ v\u00e0 $x + y + z = M$ <br\/> Th\u00ec $\\dfrac{x}{a} = \\dfrac{y}{b} = \\dfrac{z}{c} = \\dfrac{x+y+z}{a+b+c} = \\dfrac{M}{a+b+c}$ <br\/> T\u1eeb \u0111\u00f3 t\u00ecm \u0111\u01b0\u1ee3c $x, y, z$. <\/span> <br\/> <br\/> <span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/>Theo t\u00ednh ch\u1ea5t c\u1ee7a d\u00e3y t\u1ec9 s\u1ed1 b\u1eb1ng nhau, ta c\u00f3: <br\/> $\\dfrac{x}{8} = \\dfrac{y}{5} = \\dfrac{z}{12} = \\dfrac{x+y+z}{8+5+12} = \\dfrac{-100}{25} = -4 $ <br\/> Suy ra: $\\dfrac{x}{8} = -4 \\Rightarrow x = (-4).8 = -32 \\\\ \\dfrac{y}{5} = -4 \\Rightarrow y = (-4).5 = -20 \\\\ \\dfrac{z}{12} = -4 \\Rightarrow z = (-4).12 = -48 $ <br\/> V\u1eady gi\u00e1 tr\u1ecb c\u1ee7a $x, y, z$ l\u00e0: $\\begin{cases} x = -32 \\\\ y = -20 \\\\ z = -48 \\end{cases}$ <br\/> <br\/> <span class='basic_pink'> \u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 B. <\/span><\/span> ","column":1}]}]},"correct":"","level":"1","hint":"","answer":"","type":"json","extra_type":"","time":"0","user_id":"0","test":"0","date":"2019-09-30 09:22:45"},{"id":"303","post_id":"979","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 $x, y, z$ bi\u1ebft: <br\/> $\\dfrac{x}{7} = \\dfrac{y}{10} = \\dfrac{z}{13}$ v\u00e0 $x + y + z = 120$ ","select":["A. $x = 28; y = 40; z = 52 $ ","B. $x = 21; y = 30; z = 36 $ ","C. $x = 35; y = 50; z = 65 $ "],"hint":" \u00c1p d\u1ee5ng t\u00ednh ch\u1ea5t c\u1ee7a 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\/> <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\u1ed5ng,hi\u1ec7u c\u1ee7a c\u00e1c s\u1ed1 h\u1ea1ng \u0111\u00f3<\/b> <br\/> <i> Ph\u01b0\u01a1ng ph\u00e1p gi\u1ea3i <\/i> <br\/> N\u1ebfu $\\dfrac{x}{a} = \\dfrac{y}{b} = \\dfrac{z}{c}$ v\u00e0 $x + y + z = M$ <br\/> Th\u00ec $\\dfrac{x}{a} = \\dfrac{y}{b} = \\dfrac{z}{c} = \\dfrac{x+y+z}{a+b+c} = \\dfrac{M}{a+b+c}$ <br\/> T\u1eeb \u0111\u00f3 t\u00ecm \u0111\u01b0\u1ee3c $x, y, z$. <\/span> <br\/> <br\/> <span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/>Theo t\u00ednh ch\u1ea5t c\u1ee7a d\u00e3y t\u1ec9 s\u1ed1 b\u1eb1ng nhau, ta c\u00f3: <br\/> $\\dfrac{x}{7} = \\dfrac{y}{10} = \\dfrac{z}{13} = \\dfrac{x+y+z}{7+10+13} = \\dfrac{120}{30} = 4 $ <br\/> Suy ra: $\\dfrac{x}{7} = 4 \\Rightarrow x = 4.7 = 28 \\\\ \\dfrac{y}{10} = 4 \\Rightarrow y = 4.10 = 40 \\\\ \\dfrac{z}{13} = 4 \\Rightarrow z = 4.13 = 52 $ <br\/> V\u1eady gi\u00e1 tr\u1ecb c\u1ee7a $x, y, z$ l\u00e0: $\\begin{cases} x = 28 \\\\ y = 40 \\\\ z = 52 \\end{cases}$ <br\/> <br\/> <span class='basic_pink'> \u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 A. <\/span><\/span> ","column":1}]}]},"correct":"","level":"1","hint":"","answer":"","type":"json","extra_type":"","time":"0","user_id":"0","test":"0","date":"2019-09-30 09:22:45"}]}