{"common":{"save":0,"post_id":"951","level":3,"total":10,"point":10,"point_extra":0},"segment":[{"id":"41","post_id":"951","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":[[3]],"list":[{"point":10,"ques":" Cho c\u00e1c s\u1ed1 nguy\u00ean x, y th\u1ecfa m\u00e3n $\\dfrac{x}{2} = \\dfrac{3}{y}.$ \u0110\u00e1p \u00e1n n\u00e0o sau \u0111\u00e2y kh\u00f4ng ch\u00ednh x\u00e1c?","select":[" A. $x = 2; y = 3$ "," B. $x = -6; y = -1$","C. $ x= 2; y = -3$","D. $x = 1 ; y = 6$"],"hint":" Thay x, y v\u00e0o bi\u1ec3u th\u1ee9c $ \\dfrac{x}{2} = \\dfrac{y}{3}$ xem \u0111\u00e1p \u00e1n n\u00e0o kh\u00f4ng th\u1ecfa m\u00e3n","explain":" \u0110\u00e1p \u00e1n sai l\u00e0 C. <br\/> V\u00ec thay $ x= 2; y = -3$ v\u00e0o $\\dfrac{x}{2} = \\dfrac{3}{y}$ c\u00f3 <br\/> $\\dfrac{2}{2} = 1 \\neq \\dfrac{3}{-3} = -1$ <br\/> Thay $x, y$ \u1edf c\u00e1c ph\u01b0\u01a1ng \u00e1n A, B, D th\u1ea5y ch\u00fang th\u1ecfa m\u00e3n \u0111\u1eb3ng th\u1ee9c \u0111\u00e3 cho. <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 C. <\/span><\/span> ","column":2}]}]},"correct":"","level":"3","hint":"","answer":"","type":"json","extra_type":"","time":"0","user_id":"0","test":"0","date":"2019-09-30 09:22:42"},{"id":"42","post_id":"951","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":" Trong c\u00e1c ph\u00e2n s\u1ed1 sau, $ \\dfrac{-12}{15};\\dfrac{-15}{20};\\dfrac{-20}{28};\\dfrac{-27}{36} .$ Ph\u00e2n s\u1ed1 n\u00e0o bi\u1ec3u di\u1ec5n s\u1ed1 h\u1eefu t\u1ec9 $\\dfrac{3}{-4}?$ ","select":[" A. $\\dfrac{-12}{15}$ v\u00e0 $\\dfrac{-15}{20}$ "," B. $\\dfrac{-15}{20}$ v\u00e0 $\\dfrac{-20}{28}$"," C. $\\dfrac{-20}{28}$ v\u00e0 $\\dfrac{-27}{36}$","D. $\\dfrac{-15}{20}$ v\u00e0 $\\dfrac{-27}{36}$"],"hint":" R\u00fat g\u1ecdn ph\u00e2n s\u1ed1 v\u1ec1 d\u1ea1ng t\u1ed1i gi\u1ea3n r\u1ed3i so s\u00e1nh v\u1edbi $\\dfrac{3}{-4}$","explain":" \u00c1p d\u1ee5ng t\u00ednh ch\u1ea5t c\u01a1 b\u1ea3n c\u1ee7a ph\u00e2n s\u1ed1, ta c\u00f3: \\begin{align*} &\\dfrac{-12}{25} = \\dfrac{-4.3}{5.3} = \\dfrac{-4}{5} \\\\ &\\dfrac{-15}{20}= \\dfrac{3.(-5)}{-4.(-5)} = \\dfrac{-3}{4} = \\dfrac{3}{-4} \\\\ &\\dfrac{-20}{28} = \\dfrac{-5.4}{7.4} = \\dfrac{-5}{7} \\\\ &\\dfrac{-27}{36} = \\dfrac{3.(-9)}{-4.(-9)} = \\dfrac{3}{-4} \\\\ &\\text { V\u1eady c\u00e1c ph\u00e2n s\u1ed1 bi\u1ec3u di\u1ec5n s\u1ed1 h\u1eefu t\u1ec9 } \\dfrac{3}{-4}\\text { l\u00e0} : \\dfrac{-15}{20} \\text{ v\u00e0} \\dfrac{-27}{36} \\end{align*} <br\/> <span class='basic_pink'> \u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 D. <\/span><\/span> ","column":2}]}]},"correct":"","level":"3","hint":"","answer":"","type":"json","extra_type":"","time":"0","user_id":"0","test":"0","date":"2019-09-30 09:22:42"},{"id":"43","post_id":"951","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":[[3]],"list":[{"point":10,"ques":" So s\u00e1nh n\u00e0o sau \u0111\u00e2y l\u00e0 sai?","select":["A. $\\dfrac{13}{15} < \\dfrac{33}{35}$","B. $\\dfrac{-9}{11} < \\dfrac{-5}{7}$","C. $\\dfrac{-9}{7} > \\dfrac{-19}{15}$"],"hint":" Quy \u0111\u1ed3ng m\u1eabu s\u1ed1 r\u1ed3i so s\u00e1nh","explain":" <span class='basic_left'> Ta c\u00f3: $\\bullet\\dfrac{13}{15} = \\dfrac{13.7}{15.7} = \\dfrac{91}{105}; \\qquad \\dfrac{33}{35} = \\dfrac{33.3}{35.3} = \\dfrac{99}{105} $ <br\/> M\u00e0 $91 < 99 $ n\u00ean $\\dfrac{91}{105} < \\dfrac{99}{105} \\Rightarrow \\dfrac{13}{15} < \\dfrac{33}{35} \\Rightarrow$ A \u0110\u00fang. <br\/> $\\bullet\\dfrac{-9}{11} = \\dfrac{-9.7}{11.7} = \\dfrac{-63}{77}; \\qquad \\dfrac{-5}{7} = \\dfrac{-5.11}{7.11} = \\dfrac{-55}{77} $ <br\/> M\u00e0 $-63 < -55 $ n\u00ean $\\dfrac{-63}{77} < \\dfrac{-55}{77} \\Rightarrow \\dfrac{-9}{11} < \\dfrac{-5}{7} \\Rightarrow$ B \u0110\u00fang. <br\/> $\\bullet\\dfrac{-9}{7} = \\dfrac{-9.15}{7.15} = \\dfrac{-135}{105}; \\qquad \\dfrac{-19}{15} = \\dfrac{-19.7}{15.7} = \\dfrac{-133}{105} $ <br\/> M\u00e0 $-135 < -133$ n\u00ean $\\dfrac{-135}{105} < \\dfrac{-133}{105} \\Rightarrow \\dfrac{-9}{7} < \\dfrac{-19}{15} \\Rightarrow$ C Sai. <\/span> <br\/> <br\/> <span class='basic_pink'> Ch\u1ecdn \u0111\u00e1p \u00e1n C. <\/span><\/span> ","column":3}]}]},"correct":"","level":"3","hint":"","answer":"","type":"json","extra_type":"","time":"0","user_id":"0","test":"0","date":"2019-09-30 09:22:42"}]}