{"segment":[{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0110\u00fang ho\u1eb7c Sai","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":5,"ques":" T\u1ec9 s\u1ed1 c\u1ee7a hai \u0111o\u1ea1n th\u1eb3ng l\u00e0 t\u1ec9 s\u1ed1 \u0111\u1ed9 d\u00e0i c\u1ee7a ch\u00fang theo c\u00f9ng m\u1ed9t \u0111\u01a1n v\u1ecb. <b>\u0110\u00fang<\/b> hay <b>Sai<\/b>? ","select":[" A. \u0110\u00fang"," B. Sai"],"explain":" \u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0: <span class='basic_pink'>A. \u0110\u00fang<\/span>","column":2}]}],"id_ques":1651},{"time":24,"part":[{"title":"\u0110i\u1ec1n d\u1ea5u th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["="]]],"list":[{"point":5,"width":50,"content":"","type_input":"","ques":"<span class='basic_left'>Cho $\\triangle ABC$. Tr\u00ean c\u1ea1nh $AB$, $AC$ l\u1ea7n l\u01b0\u1ee3t l\u1ea5y \u0111i\u1ec3m $D$ v\u00e0 $E$ sao cho $DE \/\/ BC$. Qua $C$ k\u1ebb \u0111\u01b0\u1eddng th\u1eb3ng song song v\u1edbi $EB$, c\u1eaft $AB$ \u1edf $F$. So s\u00e1nh $AB^2$ v\u00e0 $AD.AF$ <br\/> <b>\u0110\u00e1p \u00e1n:<\/b> $AB^2$ _input_ $AD.AF$<\/span>","hint":"S\u1eed d\u1ee5ng h\u1ec7 qu\u1ea3 c\u1ee7a \u0111\u1ecbnh l\u00ed Ta-l\u00e9t \u1ee9ng v\u1edbi $\\triangle ABC$ v\u00e0 $\\triangle AFC$","explain":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai14/lv1/img\/H8C3B1_D115.png' \/><\/center> <br\/> X\u00e9t $\\triangle ABC$ c\u00f3: <br\/> $DE \/\/ BC$ (gi\u1ea3 thi\u1ebft) <br\/> $\\Rightarrow \\dfrac{AD}{AB} = \\dfrac{AE}{AC}$ (\u0111\u1ecbnh l\u00fd Ta-l\u00e9t) <b>(1)<\/b> <br\/> X\u00e9t $\\triangle AFC$ c\u00f3: <br\/> $EB \/\/ CF$ (gi\u1ea3 thi\u1ebft) <br\/> $\\Rightarrow \\dfrac{AB}{AF} = \\dfrac{AE}{AC}$ (\u0111\u1ecbnh l\u00fd Ta-l\u00e9t) <b>(2)<\/b> <br\/> T\u1eeb (1) v\u00e0 (2) $\\Rightarrow \\dfrac{AD}{AB} = \\dfrac{AB}{AF}$ <br\/> $\\Rightarrow AB.AB = AD.AF$ hay $AB^2 = AD.AF$ <br\/> V\u1eady d\u1ea5u c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 <span class='basic_pink'> \"=\"<\/span><\/span>"}]}],"id_ques":1652},{"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 \u0111\u1ed9 d\u00e0i $x$ trong h\u00ecnh sau: <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai14/lv1/img\/H8C3_B101.png' \/><\/center> ","select":[" A. $5cm$ "," B. $2,25cm$","C. $16cm$","D. $4cm$"],"explain":" <span class='basic_left'><span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span> <br\/> S\u1eed d\u1ee5ng \u0111\u1ecbnh l\u00fd Ta-l\u00e9t<\/span> <br\/> <span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> V\u00ec $EH \/\/ BC$, theo \u0111\u1ecbnh l\u00ed Ta-l\u00e9t ta c\u00f3: <br\/> $\\dfrac{AE}{EB}=\\dfrac{AH}{HC}$ hay $\\dfrac{6}{3}=\\dfrac{8}{x}$ <br\/> $\\Rightarrow x =\\dfrac{3.8}{6}=4 \\text{cm}$ <br\/> V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 <span class='basic_pink'>D. $4cm$<\/span><\/span> <br\/> <br\/> <\/span>","column":2}]}],"id_ques":1653},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"ques":" T\u00ecm \u0111\u1ed9 d\u00e0i c\u1ea1nh $BC$ trong h\u00ecnh sau: <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai14/lv1/img\/H8C3_B102.png' \/><\/center> ","select":[" A. $5$ "," B. $8$","C. $12,8$","D. $20$"],"explain":" <span class='basic_left'><span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span> <br\/> S\u1eed d\u1ee5ng \u0111\u1ecbnh l\u00fd Ta-l\u00e9t<\/span> <br\/> <span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> Ta c\u00f3: <br\/> $MN \\bot AB$ (gt) <br\/> $AC \\bot AB$ (gt) <br\/> $\\Rightarrow MN \/\/ AC$ (\u0111\u1ecbnh l\u00fd t\u1eeb vu\u00f4ng g\u00f3c \u0111\u1ebfn song song) <br\/> V\u00ec $MN \/\/ AC$, theo \u0111\u1ecbnh l\u00fd Ta-l\u00e9t ta c\u00f3: <br\/> $\\dfrac{BM}{BA}=\\dfrac{BN}{BC}$ hay $\\dfrac{5}{5+3}=\\dfrac{8}{BC}$ <br\/> $\\Rightarrow BC=\\dfrac{8.(5+3)}{5}=\\dfrac{64}{5}=12,8$ <br\/> V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 <span class='basic_pink'>C. $12,8$<\/span><\/span> <br\/> <br\/> <\/span>","column":2}]}],"id_ques":1654},{"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\u1ec9 s\u1ed1 c\u1ee7a hai \u0111o\u1ea1n th\u1eb3ng ph\u1ee5 thu\u1ed9c v\u00e0o c\u00e1ch ch\u1ecdn \u0111\u01a1n v\u1ecb \u0111o. <b>\u0110\u00fang<\/b> hay <b>sai<\/b>? ","select":[" A. \u0110\u00fang "," B. Sai"],"explain":" <span class='basic_left'>Theo ch\u00fa \u00fd t\u1ec9 s\u1ed1 c\u1ee7a hai \u0111o\u1ea1n th\u1eb3ng ta c\u00f3: <br\/> T\u1ec9 s\u1ed1 c\u1ee7a hai \u0111o\u1ea1n th\u1eb3ng <b>kh\u00f4ng<\/b> ph\u1ee5 thu\u1ed9c v\u00e0o c\u00e1ch ch\u1ecdn \u0111\u01a1n v\u1ecb \u0111o <br\/> V\u1eady ta ch\u1ecdn \u0111\u00e1p \u00e1n: <span class='basic_pink'>B. Sai<\/span>","column":2}]}],"id_ques":1655},{"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":" Vi\u1ebft t\u1ec9 s\u1ed1 c\u1ee7a c\u1eb7p \u0111o\u1ea1n th\u1eb3ng sau: $AB = 120cm$; $CD = 80cm$ ","select":[" A. $ \\dfrac{AB}{CD}=\\dfrac{120}{80}=\\dfrac{3}{2}$ "," B. $\\dfrac{AB}{CD}=\\dfrac{80}{120}=\\dfrac{2}{3}$"],"explain":" <span class='basic_left'>T\u1ec9 s\u1ed1 c\u1ee7a hai \u0111o\u1ea1n th\u1eb3ng $AB$ v\u00e0 $CD$ l\u00e0: <br\/> $\\dfrac{AB}{CD}=\\dfrac{120}{80}=\\dfrac{3}{2}$ <br\/> V\u1eady ta ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 <span class='basic_pink'> A. $ \\dfrac{AB}{CD}=\\dfrac{120}{80}=\\dfrac{3}{2}$<\/span><\/span>","column":2}]}],"id_ques":1656},{"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":" Vi\u1ebft t\u1ec9 s\u1ed1 c\u1ee7a c\u1eb7p \u0111o\u1ea1n th\u1eb3ng sau: $MN = 18,5cm$; $PQ = 12cm$ ","select":[" A. $ \\dfrac{MN}{PQ}=\\dfrac{12}{18,5}=\\dfrac{24}{37}$ "," B. $\\dfrac{MN}{PQ}=\\dfrac{18,5}{12}=\\dfrac{37}{24}$"],"explain":" <span class='basic_left'>T\u1ec9 s\u1ed1 c\u1ee7a hai \u0111o\u1ea1n th\u1eb3ng $MN$ v\u00e0 $PQ$ l\u00e0: <br\/> $\\dfrac{MN}{PQ}=\\dfrac{18,5}{12}=\\dfrac{37}{24}$ <br\/> V\u1eady ta ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 <span class='basic_pink'> B. $\\dfrac{MN}{PQ}=\\dfrac{18,5}{12}=\\dfrac{37}{24}$<\/span><\/span>","column":2}]}],"id_ques":1657},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"ques":" Hai \u0111o\u1ea1n th\u1eb3ng $AB = 15cm$, $CD = 85cm$ t\u1ec9 l\u1ec7 v\u1edbi hai \u0111o\u1ea1n th\u1eb3ng $A\u2019B\u2019 = 24cm$ v\u00e0 $C\u2019D\u2019$. \u0110o\u1ea1n th\u1eb3ng $C\u2019D\u2019$ c\u00f3 \u0111\u1ed9 d\u00e0i (theo \u0111\u01a1n v\u1ecb $cm$) l\u00e0: ","select":[" A. $84$ "," B. $53,125$","C. $136$","D. $163$"],"explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span> <br\/> S\u1eed d\u1ee5ng \u0111\u1ecbnh ngh\u0129a \u0111o\u1ea1n th\u1eb3ng t\u1ec9 l\u1ec7<\/span> <br\/> <span class='basic_left'><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> Hai \u0111o\u1ea1n th\u1eb3ng $AB$, $CD$ t\u1ec9 l\u1ec7 v\u1edbi hai \u0111o\u1ea1n th\u1eb3ng $A\u2019B\u2019$ v\u00e0 $C\u2019D\u2019$ (gi\u1ea3 thi\u1ebft) <br\/> $\\Rightarrow \\dfrac{AB}{CD}=\\dfrac{A'B'}{C'D'}$ hay $\\dfrac{15}{85}=\\dfrac{24}{C'D'}$ <br\/> $\\Rightarrow C'D'=\\dfrac{85.24}{15}=136 \\text{(cm)}$ <br\/> V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0: <span class='basic_pink'>C. $136$<\/span>","column":2}]}],"id_ques":1658},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["10"]]],"list":[{"point":5,"width":50,"content":"","type_input":"","ques":"Cho bi\u1ebft $\\dfrac{AB}{CD}=\\dfrac{2}{5} $ v\u00e0 $CD = 25cm$. T\u00ednh \u0111\u1ed9 d\u00e0i c\u1ea1nh $AB$ <br\/> \u0110\u00e1p \u00e1n: $AB = $_input_ ($cm$)","hint":"","explain":"<span class='basic_left'>Ta c\u00f3: <br\/> $\\dfrac{AB}{CD}=\\dfrac{2}{5}$ (gi\u1ea3 thi\u1ebft) <br\/> $\\Rightarrow AB=\\dfrac{2.CD}{5}=\\dfrac{2.25}{5}=10 \\text{(cm)}$ <br\/> V\u1eady s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 <span class='basic_pink'>10<\/span><\/span>"}]}],"id_ques":1659},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["24"]]],"list":[{"point":5,"width":50,"content":"","type_input":"","ques":"Cho bi\u1ebft $\\dfrac{MN}{PQ}=\\dfrac{5}{6} $ v\u00e0 $MN = 20cm$. T\u00ednh \u0111\u1ed9 d\u00e0i c\u1ea1nh $PQ$ <br\/> \u0110\u00e1p \u00e1n: $PQ =$ _input_ ($cm$)","hint":"","explain":"<span class='basic_left'>Ta c\u00f3: <br\/> $\\dfrac{MN}{PQ}=\\dfrac{5}{6} $ (gi\u1ea3 thi\u1ebft) <br\/> $\\Rightarrow PQ=\\dfrac{MN.6}{5}=\\dfrac{20.6}{5}= 24 \\text{(cm)}$ <br\/> V\u1eady s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 <span class='basic_pink'>24<\/span><\/span>"}]}],"id_ques":1660},{"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":" Cho bi\u1ebft \u0111\u1ed9 d\u00e0i c\u1ee7a $AB$ g\u1ea5p $4$ l\u1ea7n \u0111\u1ed9 d\u00e0i c\u1ea1nh $CD$ v\u00e0 \u0111\u1ed9 d\u00e0i c\u1ee7a $A\u2019B\u2019$ g\u1ea5p $5$ l\u1ea7n \u0111\u1ed9 d\u00e0i c\u1ee7a $CD$. T\u00ednh t\u1ec9 s\u1ed1 c\u1ee7a hai \u0111o\u1ea1n th\u1eb3ng $AB$ v\u00e0 $A\u2019B\u2019$. ","select":[" A. $\\dfrac{5}{4}$ "," B. $\\dfrac{4}{5}$","C. $\\dfrac{7}{8}$","D. $\\dfrac{5}{7}$"],"explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span> <br\/> S\u1eed d\u1ee5ng \u0111\u1ecbnh ngh\u0129a t\u1ec9 s\u1ed1 c\u1ee7a hai \u0111o\u1ea1n th\u1eb3ng<\/span> <br\/> <span class='basic_left'><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> Theo \u0111\u1ec1 b\u00e0i ta c\u00f3: <br\/> $AB = 4.CD$ <br\/> $A\u2019B\u2019 = 5.CD$ <br\/> T\u1ec9 s\u1ed1 c\u1ee7a hai \u0111o\u1ea1n th\u1eb3ng $AB$ v\u00e0 $A\u2019B\u2019$ l\u00e0: <br\/> $\\dfrac{AB}{A'B'}=\\dfrac{4.CD}{5.CD}=\\dfrac{4}{5}$ <br\/> V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0: <span class='basic_pink'>B. <\/span>","column":2}]}],"id_ques":1661},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"ques":" Cho bi\u1ebft \u0111\u1ed9 d\u00e0i c\u1ee7a $MN$ g\u1ea5p $7$ l\u1ea7n \u0111\u1ed9 d\u00e0i c\u1ea1nh $AB$ v\u00e0 \u0111\u1ed9 d\u00e0i c\u1ee7a $PQ$ g\u1ea5p $12$ l\u1ea7n \u0111\u1ed9 d\u00e0i c\u1ee7a $AB$. T\u00ednh t\u1ec9 s\u1ed1 c\u1ee7a hai \u0111o\u1ea1n th\u1eb3ng $MN$ v\u00e0 $PQ$ ","select":[" A. $\\dfrac{5}{7}$ "," B. $\\dfrac{12}{7}$","C. $\\dfrac{7}{12}$","D. $\\dfrac{19}{12}$"],"explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span> <br\/> S\u1eed d\u1ee5ng \u0111\u1ecbnh ngh\u0129a t\u1ec9 s\u1ed1 c\u1ee7a hai \u0111o\u1ea1n th\u1eb3ng<\/span> <br\/> <span class='basic_left'><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> Theo \u0111\u1ec1 b\u00e0i ta c\u00f3: <br\/> $MN = 7.AB$ <br\/> $PQ = 12.AB$ <br\/> T\u1ec9 s\u1ed1 c\u1ee7a hai \u0111o\u1ea1n th\u1eb3ng $MN$ v\u00e0 $PQ$ l\u00e0: <br\/> $\\dfrac{MN}{PQ}=\\dfrac{7.AB}{12.AB}=\\dfrac{7}{12}$ <br\/> V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0: <span class='basic_pink'>C. $\\dfrac{7}{12}$<\/span>","column":2}]}],"id_ques":1662},{"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":" Cho c\u00e1c \u0111o\u1ea1n th\u1eb3ng $AB = 8cm$; $CD = 6cm$; $MN = 12cm$; $PQ = x$. T\u00ecm gi\u00e1 tr\u1ecb c\u1ee7a $x$ \u0111\u1ec3 $AB$ v\u00e0 $CD$ t\u1ec9 l\u1ec7 v\u1edbi $MN$ v\u00e0 $PQ$.","select":[" A. $4cm$ "," B. $5cm$","C. $16cm$","D. $9cm$"],"hint":"","explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span> <br\/> S\u1eed d\u1ee5ng \u0111\u1ecbnh ngh\u0129a \u0111o\u1ea1n th\u1eb3ng t\u1ec9 l\u1ec7<\/span> <br\/> <span class='basic_left'><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> \u0110\u1ec3 $AB$ v\u00e0 $CD$ t\u1ec9 l\u1ec7 v\u1edbi $MN$ v\u00e0 $PQ$ <br\/> $\\Leftrightarrow \\dfrac{AB}{CD}=\\dfrac{MN}{PQ}$ (\u0111\u1ecbnh ngh\u0129a \u0111o\u1ea1n th\u1eb3ng t\u1ec9 l\u1ec7) <br\/> $\\Leftrightarrow \\dfrac{8}{6}=\\dfrac{12}{x}$ <br\/> $\\Leftrightarrow x=\\dfrac{12.6}{8} = 9 \\text{(cm)} $ <br\/> V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0: <span class='basic_pink'>D. $9\\,cm$<\/span>","column":2}]}],"id_ques":1663},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"ques":" Cho c\u00e1c \u0111o\u1ea1n th\u1eb3ng $AB = x\\,cm$; $CD = 9cm$; $MN = 7cm$; $PQ = 12cm$. T\u00ecm gi\u00e1 tr\u1ecb c\u1ee7a $x$ \u0111\u1ec3 $AB$ v\u00e0 $CD$ t\u1ec9 l\u1ec7 v\u1edbi $MN$ v\u00e0 $PQ$.","select":[" A. $4,75cm$ "," B. $15,5cm$","C. $5,25cm$","D. $9,3cm$"],"explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span> <br\/> S\u1eed d\u1ee5ng \u0111\u1ecbnh ngh\u0129a \u0111o\u1ea1n th\u1eb3ng t\u1ec9 l\u1ec7<\/span> <br\/> <span class='basic_left'><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> \u0110\u1ec3 $AB$ v\u00e0 $CD$ t\u1ec9 l\u1ec7 v\u1edbi $MN$ v\u00e0 $PQ$ <br\/> $\\Leftrightarrow \\dfrac{AB}{CD}=\\dfrac{MN}{PQ}$ (\u0111\u1ecbnh ngh\u0129a \u0111o\u1ea1n th\u1eb3ng t\u1ec9 l\u1ec7) <br\/> $\\Leftrightarrow \\dfrac{x}{9}=\\dfrac{7}{12}$ <br\/> $\\Leftrightarrow x=\\dfrac{9.7}{12} = 5,25 \\text{(cm)} $ <br\/> V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0: <span class='basic_pink'>C. $5,25cm$<\/span>","column":2}]}],"id_ques":1664},{"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":" Cho $\\triangle ABC$, tr\u00ean c\u1ea1nh $AC$ l\u1ea5y \u0111i\u1ec3m $D$ sao cho $AD = 2,4cm$, $DC = 1,6cm$. Qua $D$ k\u1ebb $DE \/\/ AB$ ($E \\in BC$). Bi\u1ebft $CB = 7cm$. T\u00ednh \u0111\u1ed9 d\u00e0i c\u1ee7a $CE$.","select":[" A. $2,8cm$ "," B. $10,5cm$","C. $4,7cm$","D. $5,6cm$"],"hint":" T\u00ednh \u0111\u1ed9 d\u00e0i c\u1ea1nh AC sau \u0111\u00f3 s\u1eed d\u1ee5ng \u0111\u1ecbnh l\u00fd Ta-l\u00e9t \u0111\u1ec3 t\u00ecm $CE$","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span> <br\/> <b>B\u01b0\u1edbc 1:<\/b> T\u00ednh $AC$ <br\/> <b>B\u01b0\u1edbc 2: <\/b>\u00c1p d\u1ee5ng \u0111\u1ecbnh l\u00ed Ta-l\u00e9t \u0111\u1ec3 \u0111\u01b0a ra h\u1ec7 th\u1ee9c: $\\dfrac{CD}{CA} = \\dfrac{CE}{CB}$ <br\/> <b>B\u01b0\u1edbc 3:<\/b> T\u1eeb h\u1ec7 th\u1ee9c \u1edf b\u01b0\u1edbc 2 t\u00ednh $CE$. <br\/> <span class='basic_left'><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai14/lv1/img\/H8C3B1_D104.png' \/><\/center> <br\/> Ta c\u00f3: $D \\in AC$ (gi\u1ea3 thi\u1ebft) <br\/> $\\Rightarrow AC = AD + DC = 2,4 + 1,6 = 4 \\text{(cm)}$ <br\/> V\u00ec $DE \/\/ AB$ (gi\u1ea3 thi\u1ebft), theo \u0111\u1ecbnh l\u00ed Ta-l\u00e9t ta c\u00f3: <br\/> $\\dfrac{CD}{CA} = \\dfrac{CE}{CB}$ hay $\\dfrac{1,6}{4} = \\dfrac{CE}{7}$ <br\/> $\\Rightarrow CE = \\dfrac{1,6.7}{4} = 2,8 \\text{(cm)}$ <br\/> V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0: <span class='basic_pink'>A. $2,8cm$<\/span>","column":2}]}],"id_ques":1665},{"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":" Cho tam gi\u00e1c $\\triangle MNP$, $E \\in MN$ v\u00e0 $F \\in MP$. Bi\u1ebft $ME = 3cm$; $EN = 4,5cm$; $MF = 6cm$ v\u00e0 $EF \/\/ NP$. T\u00ednh $FP$.","select":[" A. $2,25cm$ "," B. $4cm$","C. $4,5cm$","D. $9cm$"],"hint":" S\u1eed d\u1ee5ng \u0111\u1ecbnh l\u00fd Ta-l\u00e9t","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span> <br\/> <b>B\u01b0\u1edbc 1:<\/b>\u00c1p d\u1ee5ng \u0111\u1ecbnh l\u00ed Ta-l\u00e9t \u0111\u1ec3 \u0111\u01b0a ra h\u1ec7 th\u1ee9c: $\\dfrac{ME}{EN} = \\dfrac{MF}{FP}$ <br\/> <b>B\u01b0\u1edbc 2:<\/b> T\u1eeb h\u1ec7 th\u1ee9c \u1edf b\u01b0\u1edbc 1 t\u00ednh $FP$. <br\/> <span class='basic_left'><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span> <br\/> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai14/lv1/img\/H8C3B1_D105.png' \/><\/center> <br\/> V\u00ec $EF \/\/ NP$ (gi\u1ea3 thi\u1ebft), theo \u0111\u1ecbnh l\u00ed Ta-l\u00e9t ta c\u00f3: <br\/> $\\dfrac{ME}{EN} = \\dfrac{MF}{FP}$ hay $\\dfrac{3}{4,5} = \\dfrac{6}{FP}$ <br\/> $\\Rightarrow FP = \\dfrac{4,5 . 6}{3} = 9 \\text{(cm)}$ <br\/> V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0: <span class='basic_pink'>D. $9cm$<\/span>","column":2}]}],"id_ques":1666},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00fang hay sai","title_trans":"","temp":"true_false","correct":[["t","f","t"]],"list":[{"point":5,"image":"","col_name":["C\u00e2u h\u1ecfi:","\u0110\u00fang","Sai"],"arr_ques":[" T\u1ec9 s\u1ed1 c\u1ee7a c\u00e1c c\u1eb7p \u0111o\u1ea1n th\u1eb3ng $AB = 5cm$ v\u00e0 $CD = 7cm$ l\u00e0: $\\dfrac{AB}{CD} = \\dfrac{5}{7}$ "," T\u1ec9 s\u1ed1 c\u1ee7a c\u00e1c c\u1eb7p \u0111o\u1ea1n th\u1eb3ng $MN = 4,5cm$ v\u00e0 $PQ = 6cm$ l\u00e0: $\\dfrac{MN}{PQ} = \\dfrac{6}{4,5} = \\dfrac{4}{3}$ "," T\u1ec9 s\u1ed1 c\u1ee7a c\u00e1c c\u1eb7p \u0111o\u1ea1n th\u1eb3ng $OA = 3cm$ v\u00e0 $OB = 6cm$ l\u00e0: $\\dfrac{OA}{OB} = \\dfrac{1}{2} $ "],"hint":"","explain":["T\u1ec9 s\u1ed1 c\u1ee7a c\u00e1c c\u1eb7p \u0111o\u1ea1n th\u1eb3ng $AB = 5cm$ v\u00e0 $CD = 7cm$ l\u00e0: $\\dfrac{AB}{CD} = \\dfrac{5}{7}$ (\u0110\u00daNG)"," <br\/> T\u1ec9 s\u1ed1 c\u1ee7a c\u00e1c c\u1eb7p \u0111o\u1ea1n th\u1eb3ng $MN = 4,5cm$ v\u00e0 $PQ = 6cm$ l\u00e0: $\\dfrac{MN}{PQ} = \\dfrac{6}{4,5} = \\dfrac{4}{3}$ (SAI). V\u00ec T\u1ec9 s\u1ed1 c\u1ee7a c\u00e1c c\u1eb7p \u0111o\u1ea1n th\u1eb3ng $MN = 4,5cm$ v\u00e0 $PQ = 6cm$ l\u00e0: $\\dfrac{MN}{PQ} = \\dfrac{4,5}{6} = \\dfrac{3}{4}$ "," <br\/> T\u1ec9 s\u1ed1 c\u1ee7a c\u00e1c c\u1eb7p \u0111o\u1ea1n th\u1eb3ng $OA = 3cm$ v\u00e0 $OB = 6cm$ l\u00e0: $\\dfrac{OA}{OB} = \\dfrac{1}{2} $ (\u0110\u00daNG). V\u00ec T\u1ec9 s\u1ed1 c\u1ee7a c\u00e1c c\u1eb7p \u0111o\u1ea1n th\u1eb3ng $OA = 3cm$ v\u00e0 $OB = 6cm$ l\u00e0: $\\dfrac{OA}{OB} = \\dfrac{3}{6} = \\dfrac{1}{2} $ "]}]}],"id_ques":1667},{"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":" Cho h\u00ecnh v\u1ebd sau: <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai14/lv1/img\/H8C3B1_D106.png' \/><\/center> <br\/> H\u00e3y ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang","select":[" A. $\\dfrac{EM}{MF} = \\dfrac{EN}{NP}$ "," B. $\\dfrac{EM}{EF} = \\dfrac{EN}{EP}$","C. $\\dfrac{MF}{EF} = \\dfrac{NP}{EP}$","D. C\u1ea3 A, B, C \u0111\u1ec1u \u0111\u00fang"],"hint":" S\u1eed d\u1ee5ng \u0111\u1ecbnh l\u00fd Ta-l\u00e9t","explain":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai14/lv1/img\/H8C3B1_D106.png' \/><\/center> <br\/> V\u00ec $MN \/\/ FP$ (gi\u1ea3 thi\u1ebft), theo \u0111\u1ecbnh l\u00ed Ta-l\u00e9t ta c\u00f3: <br\/> $\\dfrac{EM}{MF} = \\dfrac{EN}{NP}$; $\\dfrac{EM}{EF} = \\dfrac{EN}{EP}$; $\\dfrac{MF}{EF} = \\dfrac{NP}{EP}$ <br\/> V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 <span class='basic_pink'>D. C\u1ea3 A, B, C \u0111\u1ec1u \u0111\u00fang<\/span><\/span>","column":2}]}],"id_ques":1668},{"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":" Cho h\u00ecnh v\u1ebd sau: <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai14/lv1/img\/H8C3B1_D107.png' \/><\/center> <br\/> H\u00e3y ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang","select":[" A. $MN \/\/ BC$ "," B. $NP \/\/ AB$","C. $MP \/\/ AC$","D. C\u1ea3 A, C \u0111\u1ec1u \u0111\u00fang"],"hint":" S\u1eed d\u1ee5ng \u0111\u1ecbnh l\u00fd Ta-l\u00e9t \u0111\u1ea3o","explain":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai14/lv1/img\/H8C3B1_D107.png' \/><\/center> <br\/> Ta c\u00f3: <br\/> $\\left.\\begin{array}{l} \\dfrac{AM}{MB} = \\dfrac{6}{2} = 3\\\\ \\dfrac{AN}{NC} = \\dfrac{4,5}{1,5} = 3 \\end{array} \\right\\}$ $\\Rightarrow \\dfrac{AM}{MB} = \\dfrac{AN}{NC}$ <br\/> $\\Rightarrow MN \/\/ BC$ (\u0111\u1ecbnh l\u00ed Ta-l\u00e9t \u0111\u1ea3o) <b>(\u0111\u00e1p \u00e1n A \u0111\u00fang)<\/b> <br\/> $\\left.\\begin{array}{l} \\dfrac{BM}{MA} = \\dfrac{2}{6} = \\dfrac{1}{3}\\\\ \\dfrac{BP}{PC} = \\dfrac{2,25}{6,75} = \\dfrac{1}{3} \\end{array} \\right\\}$ $\\Rightarrow \\dfrac{BM}{MA} = \\dfrac{BP}{PC}$ <br\/> $\\Rightarrow MP \/\/ AC$ (\u0111\u1ecbnh l\u00ed Ta-l\u00e9t \u0111\u1ea3o) <b>(\u0111\u00e1p \u00e1n C \u0111\u00fang)<\/b> <br\/> $\\left.\\begin{array}{l} \\dfrac{CP}{PB} = \\dfrac{6.75}{2,25} = 3\\\\ \\dfrac{CN}{NA} = \\dfrac{1,5}{4,5} = \\dfrac{1}{3} \\end{array} \\right\\}$ $\\Rightarrow \\dfrac{CP}{PB} \\neq \\dfrac{CN}{NA}$ <br\/> $\\Rightarrow$ NP v\u00e0 AB kh\u00f4ng song song v\u1edbi nhau <b>(\u0111\u00e1p \u00e1n B sai)<\/b> <br\/> V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 <span class='basic_pink'>D. C\u1ea3 A, C \u0111\u1ec1u \u0111\u00fang<\/span><\/span>","column":2}]}],"id_ques":1669},{"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":" Cho h\u00ecnh v\u1ebd sau: <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai14/lv1/img\/H8C3B1_D108.png' \/><\/center> <br\/> Bi\u1ebft $\\dfrac{ME}{MN} = \\dfrac{2}{5}$. T\u00ednh $NP$.","select":[" A. $NP = 12cm$ "," B. $NP = 15cm$","C. $NP = 28cm$","D. $NP = 24cm$"],"hint":" S\u1eed d\u1ee5ng h\u1ec7 qu\u1ea3 c\u1ee7a \u0111\u1ecbnh l\u00fd Ta-l\u00e9t","explain":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai14/lv1/img\/H8C3B1_D108.png' \/><\/center> <br\/> $\\triangle MNP$ c\u00f3: <br\/> $\\left.\\begin{array}{l} EF \/\/ NP \\text{(gi\u1ea3 thi\u1ebft)}\\\\ E \\in MN; F \\in MP \\text{(gi\u1ea3 thi\u1ebft)} \\end{array} \\right\\}$ <br\/> $\\Rightarrow \\dfrac{ME}{MN} = \\dfrac{EF}{NP}$ (h\u1ec7 qu\u1ea3 c\u1ee7a \u0111\u1ecbnh l\u00ed Ta-l\u00e9t) <br\/> $\\Rightarrow \\dfrac{2}{5} = \\dfrac{4,8}{NP}$ <br\/> $\\Rightarrow NP = \\dfrac{5.4,8}{2} = 12 \\text{(cm)}$ <br\/> <br\/> V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 <span class='basic_pink'>A. $NP = 12cm$<\/span><\/span>","column":2}]}],"id_ques":1670}],"lesson":{"save":0,"level":1}}