{"segment":[{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t <br\/> Kh\u1eb3ng \u0111\u1ecbnh sau \u0111\u00e2y <b> \u0110\u00fang<\/b> hay <b> Sai <\/b>","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":5,"ques":" <span class='basic_left'> Di\u1ec7n t\u00edch h\u00ecnh thang b\u1eb1ng n\u1eeda t\u00edch \u0111\u1ed9 d\u00e0i hai \u0111\u00e1y c\u1ee7a n\u00f3. <\/span>","select":[" \u0110\u00fang"," Sai"],"explain":" <span class='basic_left'> Di\u1ec7n t\u00edch h\u00ecnh thang b\u1eb1ng n\u1eeda t\u00edch \u0111\u1ed9 d\u00e0i \u0111\u01b0\u1eddng cao v\u1edbi t\u1ed5ng hai \u0111\u00e1y c\u1ee7a n\u00f3. <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 Sai. <\/span> <\/span> ","column":2}]}],"id_ques":1591},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t <br\/> Kh\u1eb3ng \u0111\u1ecbnh sau \u0111\u00e2y <b> \u0110\u00fang<\/b> hay <b> Sai <\/b>","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":5,"ques":" <span class='basic_left'> Di\u1ec7n t\u00edch h\u00ecnh thoi b\u1eb1ng n\u1eeda t\u00edch hai \u0111\u01b0\u1eddng ch\u00e9o c\u1ee7a n\u00f3.<\/span>","select":[" \u0110\u00fang"," Sai"],"explain":" <span class='basic_left'> Di\u1ec7n t\u00edch h\u00ecnh thoi b\u1eb1ng n\u1eeda t\u00edch hai \u0111\u01b0\u1eddng ch\u00e9o c\u1ee7a n\u00f3. <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 \u0110\u00fang. <\/span> <\/span> ","column":2}]}],"id_ques":1592},{"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":" <span class='basic_left'> M\u1ed9t h\u00ecnh thang c\u00f3 \u0111\u00e1y nh\u1ecf l\u00e0 $4 cm$, \u0111\u01b0\u1eddng cao l\u00e0 $5 cm$. Bi\u1ebft di\u1ec7n t\u00edch h\u00ecnh thang l\u00e0 $40 cm^2$ th\u00ec \u0111\u1ed9 d\u00e0i \u0111\u00e1y l\u1edbn l\u00e0: <\/span>","select":["A. $20\\,cm$ ","B. $16\\,cm$","C. $15\\,cm$","D. $12\\,cm$"],"explain":" <span class='basic_left'> G\u1ecdi $S$ l\u00e0 di\u1ec7n t\u00edch h\u00ecnh thang. <br\/> $h$ l\u00e0 \u0111\u1ed9 d\u00e0i \u0111\u01b0\u1eddng cao. <br\/> $a, b$ l\u1ea7n l\u01b0\u1ee3t l\u00e0 \u0111\u00e1y nh\u1ecf v\u00e0 \u0111\u00e1y l\u1edbn c\u1ee7a h\u00ecnh thang. <br\/> Khi \u0111\u00f3, ta c\u00f3: <br\/> $S=\\dfrac{1}{2}.h.(a + b)$ <br\/> $\\Rightarrow h(a + b) =2S$ <br\/> $\\Rightarrow h(a + b)=80$ <br\/> $\\Rightarrow 5.(4+b)=80$ <br\/> $\\Rightarrow b=80:5-4$ <br\/> $\\Rightarrow b=12\\,(cm)$ <br\/> \u0110\u00e1y l\u1edbn h\u00ecnh thang d\u00e0i $12 cm$.<br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 D. <\/span> <\/span> ","column":2}]}],"id_ques":1593},{"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":" <span class='basic_left'> H\u00ecnh thang c\u00f3 \u0111\u1ed9 d\u00e0i \u0111\u01b0\u1eddng cao l\u00e0 $h$, \u0111\u00e1y nh\u1ecf l\u00e0 $a$ v\u00e0 \u0111\u00e1y l\u1edbn l\u00e0 $b$. Bi\u1ebft $h=5\\,cm; b=9\\,cm$. Bi\u1ebft di\u1ec7n t\u00edch h\u00ecnh thang l\u00e0 $30\\,cm^2$. \u0110\u1ed9 d\u00e0i \u0111\u00e1y nh\u1ecf $a$ l\u00e0: <\/span>","select":["A. $3,5\\,cm$ ","B. $3\\,cm$","C. $2,5\\,cm$","D. $4\\,cm$"],"explain":" <span class='basic_left'> G\u1ecdi $S$ l\u00e0 di\u1ec7n t\u00edch h\u00ecnh thang. <br\/> Khi \u0111\u00f3, ta c\u00f3: <br\/> $S=\\dfrac{1}{2}.h.(a + b)$ <br\/> $\\Rightarrow h(a + b) =2S$ <br\/> $\\Rightarrow 5.(a+9)=60$ <br\/> $\\Rightarrow a=60:5-9$ <br\/> $\\Rightarrow a=3\\,(cm)$ <br\/> \u0110\u00e1y nh\u1ecf h\u00ecnh thang d\u00e0i $3 cm$.<br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 B. <\/span> <\/span> ","column":2}]}],"id_ques":1594},{"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":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai12/lv1/img\/H822_D1_1.jpg' \/><\/center> H\u00ecnh b\u00ecnh h\u00e0nh $ABCD$ c\u00f3 \u0111\u01b0\u1eddng cao $AH=5\\,cm$, $CD=10\\,cm$. Di\u1ec7n t\u00edch h\u00ecnh b\u00ecnh h\u00e0nh $ABCD$ l\u00e0: <\/span>","select":["A. $50\\,cm^2$ ","B. $66\\,cm^2$","C. $25,5\\,cm^2$","D. $35\\,cm^2$"],"explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai12/lv1/img\/H822_D1_1.jpg' \/><\/center> Di\u1ec7n t\u00edch h\u00ecnh b\u00ecnh h\u00e0nh $ABCD$ l\u00e0: <br\/> $S_{ABCD}=AH.CD$ <br\/> $=5.10=50\\,(cm^2)$ <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 A. <\/span> <br\/> <b> L\u01b0u \u00fd: <\/b> <i> Di\u1ec7n t\u00edch h\u00ecnh b\u00ecnh h\u00e0nh b\u1eb1ng t\u00edch \u0111\u01b0\u1eddng cao v\u1edbi \u0111\u00e1y t\u01b0\u01a1ng \u1ee9ng. <\/i> <\/span> ","column":2}]}],"id_ques":1595},{"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":" <span class='basic_left'> H\u00ecnh b\u00ecnh h\u00e0nh c\u00f3 di\u1ec7n t\u00edch l\u00e0 $36\\,cm^2$, m\u1ed9t c\u1ea1nh c\u00f3 \u0111\u1ed9 d\u00e0i l\u00e0 $24\\,cm$. \u0110\u01b0\u1eddng cao t\u01b0\u01a1ng \u1ee9ng v\u1edbi c\u1ea1nh \u0111\u00e3 cho l\u00e0: <\/span>","select":["A. $1,5\\,cm$ ","B. $1,2\\,cm$","C. $0,75\\,cm$","D. $6\\,cm$"],"explain":" <span class='basic_left'> \u0110\u1ed9 d\u00e0i \u0111\u01b0\u1eddng cao t\u01b0\u01a1ng \u1ee9ng v\u1edbi c\u1ea1nh \u0111\u00e3 cho l\u00e0: <br\/> $36:24=1,5\\,(cm)$ <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 A. <\/span> <br\/> <b> L\u01b0u \u00fd: <\/b> <i> Di\u1ec7n t\u00edch h\u00ecnh b\u00ecnh h\u00e0nh b\u1eb1ng t\u00edch \u0111\u01b0\u1eddng cao v\u1edbi \u0111\u00e1y t\u01b0\u01a1ng \u1ee9ng. <\/i> <\/span> ","column":2}]}],"id_ques":1596},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["20"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<span class='basic_left'> H\u00ecnh thoi c\u00f3 \u0111\u1ed9 d\u00e0i hai \u0111\u01b0\u1eddng ch\u00e9o l\u00e0 $5\\,cm$ v\u00e0 $8\\, cm$. T\u00ednh di\u1ec7n t\u00edch h\u00ecnh thoi \u0111\u00f3. <br\/> <b> \u0110\u00e1p \u00e1n: <\/b> $S=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}\\,(cm^2)$ <\/span> ","explain":" <span class='basic_left'> Di\u1ec7n t\u00edch h\u00ecnh thoi \u0111\u00e3 cho l\u00e0: <br\/> $\\dfrac{1}{2}.5.8=20\\,(cm^2)$ <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $20$. <\/span> <br\/> <b> L\u01b0u \u00fd: <\/b> <i> Di\u1ec7n t\u00edch h\u00ecnh thoi b\u1eb1ng n\u1eeda t\u00edch hai \u0111\u01b0\u1eddng ch\u00e9o c\u1ee7a n\u00f3. <\/i> <\/span> "}]}],"id_ques":1597},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["20"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<span class='basic_left'> H\u00ecnh thoi c\u00f3 di\u1ec7n t\u00edch l\u00e0 $150\\,cm^2$. \u0110\u1ed9 d\u00e0i \u0111\u01b0\u1eddng ch\u00e9o th\u1ee9 nh\u1ea5t l\u00e0 $15\\, cm$. <br\/> T\u00ednh \u0111\u1ed9 d\u00e0i \u0111\u01b0\u1eddng ch\u00e9o th\u1ee9 hai <br\/> <b> \u0110\u00e1p \u00e1n: <\/b> $\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}\\,cm$ <\/span> ","explain":" <span class='basic_left'> \u0110\u1ed9 d\u00e0i \u0111\u01b0\u1eddng ch\u00e9o th\u1ee9 hai l\u00e0: <br\/> $(2.150):15=20\\,(cm)$ <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $20$. <\/span> <br\/> <b> L\u01b0u \u00fd: <\/b> <i> Di\u1ec7n t\u00edch h\u00ecnh thoi b\u1eb1ng n\u1eeda t\u00edch hai \u0111\u01b0\u1eddng ch\u00e9o c\u1ee7a n\u00f3. <\/i> <\/span> "}]}],"id_ques":1598},{"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":" <span class='basic_left'> Cho h\u00ecnh thang c\u00f3 di\u1ec7n t\u00edch l\u00e0 $24\\,cm^2$, \u0111\u01b0\u1eddng cao d\u00e0i $6 \\,cm$. \u0110\u1ed9 d\u00e0i \u0111\u00e1y l\u1edbn h\u01a1n \u0111\u1ed9 d\u00e0i \u0111\u00e1y nh\u1ecf $3 \\,cm$. \u0110\u1ed9 d\u00e0i hai \u0111\u00e1y c\u1ee7a h\u00ecnh thang l\u00e0: <\/span>","select":["A. $5 \\,cm$ v\u00e0 $8 \\,cm$ ","B. $6\\, cm$ v\u00e0 $3 \\,cm$","C. $5,5 \\,cm$ v\u00e0 $2,5 \\,cm$","D. K\u1ebft qu\u1ea3 kh\u00e1c"],"hint":" T\u00ecm t\u1ed5ng v\u00e0 hi\u1ec7u c\u1ee7a hai \u0111\u00e1y r\u1ed3i suy ra \u0111\u1ed9 d\u00e0i c\u1ee7a ch\u00fang","explain":" <span class='basic_left'> G\u1ecdi \u0111\u1ed9 d\u00e0i hai \u0111\u00e1y c\u1ee7a h\u00ecnh thang l\u00e0 $a$ v\u00e0 $b$ $(a > b > 0)$ $(cm)$ <br\/> Ta c\u00f3: $S=\\dfrac{1}{2}.6.(a+b)$ <br\/> $\\Rightarrow 6(a+b)=2S$ <br\/> $\\Rightarrow 6(a+b)=2.24$ <br\/> $\\Rightarrow a+b=8$ (1) <br\/> M\u1eb7t kh\u00e1c: $a-b=3$ (2) <br\/> T\u1eeb (1) v\u00e0 (2) ta c\u00f3: <br\/> $\\begin{aligned} & \\left\\{ \\begin{aligned} & a+b=8 \\\\ & a-b=3 \\\\ \\end{aligned} \\right. \\\\ & \\Rightarrow \\left\\{ \\begin{aligned} & 2a=11 \\\\ & a-b=3 \\\\ \\end{aligned} \\right. \\\\ & \\Rightarrow \\left\\{ \\begin{aligned} & a=5,5 \\\\ & b=2,5 \\\\ \\end{aligned} \\right. \\\\ \\end{aligned}$ <br\/> \u0110\u1ed9 d\u00e0i hai \u0111\u00e1y c\u1ee7a h\u00ecnh thang l\u00e0 $5,5 \\,cm$ v\u00e0 $2,5\\, cm$. <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 C. <\/span> <br\/> <b> L\u01b0u \u00fd: <\/b> <i> Di\u1ec7n t\u00edch h\u00ecnh thang b\u1eb1ng n\u1eeda t\u00edch \u0111\u01b0\u1eddng cao v\u1edbi t\u1ed5ng hai \u0111\u00e1y. <\/i> <\/span> ","column":2}]}],"id_ques":1599},{"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":" <span class='basic_left'> H\u00ecnh thoi $ABCD$ c\u00f3 $AC=10\\,cm; AB=13\\,cm$. Di\u1ec7n t\u00edch h\u00ecnh thoi l\u00e0: <\/span>","select":["A. $120\\,cm^2$ ","B. $130\\,cm^2$","C. $240\\,cm^2$","D. $180\\,cm^2$"],"hint":" T\u00ednh \u0111\u1ed9 d\u00e0i hai \u0111\u01b0\u1eddng ch\u00e9o c\u1ee7a h\u00ecnh thoi. ","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai12/lv1/img\/H822_D1_2.jpg' \/><\/center> G\u1ecdi $O=AC\\cap BD$ <br\/> Theo gi\u1ea3 thi\u1ebft: $AC=10\\,cm \\Rightarrow AO=5\\,(cm)$ (t\u00ednh ch\u1ea5t) <br\/> X\u00e9t $\\Delta ABO$ vu\u00f4ng t\u1ea1i $O$, ta c\u00f3: <br\/> $AB^2=AO^2+BO^2$ (\u0111\u1ecbnh l\u00ed Pi - ta - go) <br\/> $\\Rightarrow 13^2=5^2+BO^2$ <br\/> $\\Rightarrow BO^2=13^2-5^2=144$ <br\/> $\\Rightarrow BO=12\\,(cm)$ <br\/> M\u00e0 $BD=2BO \\Rightarrow BD=24\\,(cm)$ <br\/> Di\u1ec7n t\u00edch h\u00ecnh thoi l\u00e0: <br\/> $\\dfrac{1}{2}AC.BD$$=\\dfrac{1}{2}.10.24$$=120\\,(cm^2)$ <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 A. <\/span> <br\/> <b> L\u01b0u \u00fd: <\/b> <i> Di\u1ec7n t\u00edch h\u00ecnh thoi b\u1eb1ng n\u1eeda t\u00edch hai \u0111\u01b0\u1eddng ch\u00e9o c\u1ee7a n\u00f3.<\/i> <\/span> ","column":2}]}],"id_ques":1600},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"\u0110\u1ec1 chung cho hai c\u00e2u","temp":"fill_the_blank","correct":[[["16"],["30"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai12/lv1/img\/H822_D1_3.jpg' \/><\/center> Cho h\u00ecnh thoi $ABCD$ c\u00f3 c\u1ea1nh l\u00e0 $17\\,cm$ nh\u01b0 h\u00ecnh v\u1ebd tr\u00ean. T\u1ed5ng hai \u0111\u01b0\u1eddng ch\u00e9o l\u00e0 $46 \\,cm$ $(AC > BD)$. <br\/> <b> C\u00e2u 1: <\/b> T\u00ednh \u0111\u1ed9 d\u00e0i $BD$ v\u00e0 $AC$. <br\/> <br\/> <b> \u0110\u00e1p \u00e1n: <\/b> <br\/> $BD=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}\\,(cm)$ <br\/> $AC=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}\\,(cm)$ <\/span> ","hint":" T\u00ecm gi\u00e1 tr\u1ecb c\u1ee7a $x+y$ v\u00e0 $xy$.","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai12/lv1/img\/H822_D1_3.jpg' \/><\/center> Theo h\u00ecnh v\u1ebd \u0111\u00e3 cho $OA=x; OB=y$. <br\/> $\\Rightarrow x^2+y^2=17^2$ <br\/> M\u00e0 $AC+BD=46 \\Rightarrow x+y=23$ (1) <br\/> $\\Rightarrow (x+y)^2=23^2$ <br\/> $\\Rightarrow x^2+y^2+2xy=23^2$ <br\/> $\\Rightarrow 17^2+2xy=23^2$ <br\/> $\\Rightarrow xy=120$ (2) <br\/> T\u1eeb (1) v\u00e0 (2) suy ra: <br\/> $\\left\\{ \\begin{aligned} & x+y=23 \\\\ & xy=120 \\\\ \\end{aligned} \\right.\\Rightarrow \\left\\{ \\begin{aligned} & y=23-x \\\\ & x(23-x)=120 \\\\ \\end{aligned} \\right.\\Rightarrow \\left\\{ \\begin{aligned} & y=23-x \\\\ & -x^2+23x-120=0 \\\\ \\end{aligned} \\right.\\Rightarrow \\left\\{ \\begin{aligned} & x=15 \\\\ & y=8 \\\\ \\end{aligned} \\right.$ <br\/> M\u00e0: $BD=2y=2.8=16\\,(cm)$ <br\/> $AC=2x=2.15=30\\,(cm)$. <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $16$ v\u00e0 $30$. <\/span> <\/span> "}]}],"id_ques":1601},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"\u0110\u1ec1 chung cho hai c\u00e2u","temp":"fill_the_blank","correct":[[["240"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai12/lv1/img\/H822_D1_3.jpg' \/><\/center> Cho h\u00ecnh thoi $ABCD$ c\u00f3 c\u1ea1nh l\u00e0 $17\\, cm$ nh\u01b0 h\u00ecnh v\u1ebd tr\u00ean. T\u1ed5ng hai \u0111\u01b0\u1eddng ch\u00e9o l\u00e0 $46 \\,cm$ $(AC > BD)$. <br\/> <b> C\u00e2u 2: <\/b> T\u00ednh di\u1ec7n t\u00edch h\u00ecnh thoi $ABCD$. <br\/> <b> \u0110\u00e1p \u00e1n: <\/b> $S_{ABCD}=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}\\,(cm^2)$ <\/span> ","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai12/lv1/img\/H822_D1_3.jpg' \/><\/center> Theo c\u00e2u 1, ta c\u00f3: $AC=30\\,cm; BD=16\\,(cm)$ <br\/> Di\u1ec7n t\u00edch h\u00ecnh thoi $ABCD$ l\u00e0: <br\/> $S_{ABCD}=\\dfrac{1}{2}.AC.BD$ <br\/> $=\\dfrac{1}{2}.30.16$ <br\/> $=240\\,(cm^2)$ <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $240$. <\/span> <\/span> "}]}],"id_ques":1602},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"\u0110\u1ec1 chung cho hai c\u00e2u","temp":"fill_the_blank","correct":[[["2"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<span class='basic_left'> Cho h\u00ecnh thang $ABCD$ c\u00f3 $\\widehat{A}=\\widehat{D}=90^o$; $\\widehat{C}=45^o$; $AB=1\\,cm$; $ CD=3\\,cm$. <br\/> <b> C\u00e2u 1: <\/b> T\u00ednh $AD$. <br\/> <b> \u0110\u00e1p \u00e1n: <\/b> $AD=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}\\,(cm)$ <\/span> ","hint":" K\u1ebb $BH \\bot DC$ t\u1ea1i $H$. ","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai12/lv1/img\/H822_D1_4.jpg' \/><\/center> K\u1ebb $BH \\bot DC$ t\u1ea1i $H$. <br\/> $\\Rightarrow \\widehat{A}=\\widehat{D}=\\widehat{H}=90^o$ <br\/> Do \u0111\u00f3: $ABHD$ l\u00e0 h\u00ecnh ch\u1eef nh\u1eadt <br\/> $\\Rightarrow AB=DH=1\\,cm$; $AD=BH$ (t\u00ednh ch\u1ea5t) <br\/> Ta c\u00f3: $\\Delta BHC$ vu\u00f4ng t\u1ea1i $H$, $\\widehat{C}=45^o$ <br\/> $\\Rightarrow \\Delta BHC$ vu\u00f4ng c\u00e2n t\u1ea1i $H$. <br\/> $\\Rightarrow BH=HC=DC-DH=3-1=2\\,(cm)$ <br\/> Do \u0111\u00f3: $AD=2\\,(cm)$ <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $2$. <\/span> <\/span> "}]}],"id_ques":1603},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"\u0110\u1ec1 chung cho hai c\u00e2u","temp":"fill_the_blank","correct":[[["4"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<span class='basic_left'> Cho h\u00ecnh thang $ABCD$ c\u00f3 $\\widehat{A}=\\widehat{D}=90^o$; $\\widehat{C}=45^o$; $AB=1\\,cm$; $ CD=3\\,cm$ <br\/> <b> C\u00e2u 2: <\/b> T\u00ednh di\u1ec7n t\u00edch h\u00ecnh thang $ABCD$. <br\/> <b> \u0110\u00e1p \u00e1n: <\/b> $S_{ABCD}=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}\\,(cm^2)$ <\/span> ","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai12/lv1/img\/H822_D1_4.jpg' \/><\/center> Theo c\u00e2u 1, ta \u0111\u00e3 t\u00ednh \u0111\u01b0\u1ee3c: $BH=2\\,(cm)$ <br\/> Di\u1ec7n t\u00edch h\u00ecnh thang $ABCD$ l\u00e0: <br\/> $S_{ABCD}=\\dfrac{1}{2}.BH(AB+DC)$ <br\/> $=\\dfrac{1}{2}.2.(1+3)=4\\,(cm^2)$ <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $4$. <\/span> <\/span> "}]}],"id_ques":1604},{"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":" <span class='basic_left'> N\u1ebfu h\u00ecnh thang ch\u1ec9 c\u00f3 \u0111\u01b0\u1eddng cao t\u0103ng l\u00ean $10$ l\u1ea7n th\u00ec di\u1ec7n t\u00edch c\u1ee7a h\u00ecnh thang \u0111\u00f3 t\u0103ng l\u00ean: <\/span>","select":["A. $10$ l\u1ea7n ","B. $20$ l\u1ea7n","C. $5$ l\u1ea7n","D. $2$ l\u1ea7n"],"hint":" T\u00ednh di\u1ec7n t\u00edch l\u00fac \u0111\u1ea7u v\u00e0 di\u1ec7n t\u00edch l\u00fac sau r\u1ed3i so s\u00e1nh.","explain":" <span class='basic_left'> G\u1ecdi $a, b, h$ l\u1ea7n l\u01b0\u1ee3t l\u00e0 \u0111\u00e1y l\u1edbn, \u0111\u00e1y nh\u1ecf, \u0111\u01b0\u1eddng cao t\u01b0\u01a1ng \u1ee9ng trong h\u00ecnh thang $(a > b > 0; h > 0)$. <br\/> Di\u1ec7n t\u00edch h\u00ecnh thang l\u00fac \u0111\u1ea7u l\u00e0: <br\/> $S_{\\text{\u0111}}=\\dfrac{1}{2}.h.(a+b)$ <br\/> Ch\u1ec9 c\u00f3 \u0111\u01b0\u1eddng cao t\u0103ng l\u00ean $10$ l\u1ea7n, th\u00ec di\u1ec7n t\u00edch h\u00ecnh thang l\u00fac sau l\u00e0: <br\/> $S_{s}=\\dfrac{1}{2}.10h.(a+b)$ <br\/> $=10.\\dfrac{1}{2}.h.(a+b)$ <br\/> $=10S_{\\text{\u0111}}$ <br\/> $\\Rightarrow S_s=10S_{\\text{\u0111}}$ <br\/> V\u1eady di\u1ec7n t\u00edch c\u1ee7a h\u00ecnh thang t\u0103ng l\u00ean $10$ l\u1ea7n. <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 A. <\/span> <\/span> ","column":2}]}],"id_ques":1605},{"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":" <span class='basic_left'> N\u1ebfu h\u00ecnh b\u00ecnh h\u00e0nh c\u00f3 \u0111\u1ed9 d\u00e0i \u0111\u01b0\u1eddng cao gi\u1ea3m \u0111i $5$ l\u1ea7n, c\u1ea1nh t\u01b0\u01a1ng \u1ee9ng v\u1edbi \u0111\u01b0\u1eddng cao t\u0103ng l\u00ean $10$ l\u1ea7n th\u00ec di\u1ec7n t\u00edch h\u00ecnh b\u00ecnh h\u00e0nh s\u1ebd: <\/span>","select":["A. T\u0103ng l\u00ean $5$ l\u1ea7n ","B. T\u0103ng l\u00ean $2$ l\u1ea7n","C. Gi\u1ea3m \u0111i $5$ l\u1ea7n","D. Gi\u1ea3m \u0111i $2$ l\u1ea7n"],"hint":" T\u00ednh di\u1ec7n t\u00edch l\u00fac \u0111\u1ea7u v\u00e0 di\u1ec7n t\u00edch l\u00fac sau r\u1ed3i so s\u00e1nh.","explain":" <span class='basic_left'> G\u1ecdi $h, a$ l\u1ea7n l\u01b0\u1ee3t l\u00e0 \u0111\u1ed9 d\u00e0i \u0111\u01b0\u1eddng cao v\u00e0 \u0111\u00e1y t\u01b0\u01a1ng \u1ee9ng trong h\u00ecnh b\u00ecnh h\u00e0nh $( h; a > 0)$. <br\/> Di\u1ec7n t\u00edch h\u00ecnh b\u00ecnh h\u00e0nh l\u00fac \u0111\u1ea7u l\u00e0: <br\/> $S_{\\text{\u0111}}=h.a$ <br\/> Di\u1ec7n t\u00edch h\u00ecnh b\u00ecnh h\u00e0nh sau khi gi\u1ea3m \u0111\u1ed9 d\u00e0i \u0111\u01b0\u1eddng cao \u0111i $5$ l\u1ea7n v\u00e0 t\u0103ng c\u1ea1nh \u0111\u00e1y t\u01b0\u01a1ng \u1ee9ng l\u00ean $10$ l\u1ea7n l\u00e0: <br\/> $S_{s}=\\dfrac{h}{5}.10a$ <br\/> $=2ha$ <br\/> $=2S_{\\text{\u0111}}$ <br\/> Do \u0111\u00f3: $S_s=2S_{\\text{\u0111}}$ <br\/> V\u1eady di\u1ec7n t\u00edch h\u00ecnh b\u00ecnh h\u00e0nh t\u0103ng l\u00ean $2$ l\u1ea7n. <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 B. <\/span> <\/span> ","column":2}]}],"id_ques":1606},{"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":" <span class='basic_left'>H\u00ecnh thoi c\u00f3 \u0111\u1ed9 d\u00e0i hai \u0111\u01b0\u1eddng ch\u00e9o \u0111\u1ec1u t\u0103ng l\u00ean $4$ l\u1ea7n th\u00ec di\u1ec7n t\u00edch h\u00ecnh thoi \u0111\u00f3 s\u1ebd: <\/span>","select":["A. T\u0103ng l\u00ean $4$ l\u1ea7n","B. T\u0103ng l\u00ean $8$ l\u1ea7n","C. T\u0103ng l\u00ean $12$ l\u1ea7n","D. T\u0103ng l\u00ean $16$ l\u1ea7n"],"hint":" T\u00ednh di\u1ec7n t\u00edch l\u00fac \u0111\u1ea7u v\u00e0 di\u1ec7n t\u00edch l\u00fac sau r\u1ed3i so s\u00e1nh.","explain":" <span class='basic_left'> G\u1ecdi $d_1; d_2$ l\u1ea7n l\u01b0\u1ee3t l\u00e0 \u0111\u1ed9 d\u00e0i hai \u0111\u01b0\u1eddng ch\u00e9o trong h\u00ecnh thoi $( d_1;d_2 > 0)$. <br\/> Di\u1ec7n t\u00edch h\u00ecnh thoi l\u00fac \u0111\u1ea7u l\u00e0: <br\/> $S_{\\text{\u0111}}=\\dfrac{1}{2}d_1d_2$ <br\/> Di\u1ec7n t\u00edch h\u00ecnh thoi sau khi \u0111\u1ed9 d\u00e0i hai \u0111\u01b0\u1eddng ch\u00e9o \u0111\u1ec1u t\u0103ng l\u00ean $4$ l\u1ea7n l\u00e0: <br\/> $S_{s}=\\dfrac{1}{2}.4d_1.4d_2$ <br\/> $=16.\\dfrac{1}{2}d_1d_2$ <br\/> $=16S_{\\text{\u0111}}$ <br\/> Do \u0111\u00f3: $S_s=16S_{\\text{\u0111}}$ <br\/> V\u1eady di\u1ec7n t\u00edch h\u00ecnh thoi t\u0103ng l\u00ean $16$ l\u1ea7n. <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 D. <\/span> <\/span> ","column":2}]}],"id_ques":1607},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["7912"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<span class='basic_left'> T\u00ednh di\u1ec7n t\u00edch t\u1ee9 gi\u00e1c $ABCD$ c\u00f3 c\u00e1c k\u00edch th\u01b0\u1edbc b\u1eb1ng milimet nh\u01b0 trong h\u00ecnh v\u1ebd sau <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai12/lv1/img\/H822_D1_5.jpg' \/><\/center> <br\/> <b> \u0110\u00e1p \u00e1n: <\/b> $S_{ABCD}=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}\\,(mm^2)$ <\/span> ","hint":" L\u1ea5y $AH\\bot DC$ t\u1ea1i $H;\\,\\,BK\\bot DC$ t\u1ea1i $K$. <br\/> ${{S}_{ABCD}}={{S}_{ADH}}+{{S}_{ABKH}}+{{S}_{BKC}}$","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai12/lv1/img\/H822_D1_5.jpg' \/><\/center> L\u1ea5y $AH\\bot DC$ t\u1ea1i $H;\\,\\,BK\\bot DC$ t\u1ea1i $K$ <br\/> Ta c\u00f3: ${{S}_{ADH}}=\\dfrac{1}{2}AH.DH$<br\/> $=\\dfrac{1}{2}.74.36=1332\\,\\,\\left( m{{m}^{2}} \\right)$ <br\/> ${{S}_{BKC}}=\\dfrac{1}{2}BK.KC$<br\/>$=\\dfrac{1}{2}.56.40=1120\\,\\,\\left( m{{m}^{2}} \\right)$ <br\/> ${{S}_{ABKH}}=\\dfrac{1}{2}\\left( AH+BK \\right).HK$<br\/>$=\\dfrac{1}{2}\\left( 74+56 \\right).84=5460\\,\\,\\left( m{{m}^{2}} \\right)$ <br\/> ${{S}_{ABCD}}$$={{S}_{ADH}}+{{S}_{ABKH}}+{{S}_{BKC}}$<br\/>$=1332+1120+5460=7912\\,\\,\\left( m{{m}^{2}} \\right)$ <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $7912$. <\/span> <\/span> "}]}],"id_ques":1608},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t ","title_trans":"\u0110\u1ec1 chung cho hai c\u00e2u","temp":"multiple_choice","correct":[[4]],"list":[{"point":5,"ques":" <span class='basic_left'>H\u00ecnh vu\u00f4ng $ABCD$ c\u00f3 \u0111\u01b0\u1eddng ch\u00e9o b\u1eb1ng $4 \\,cm$. Tr\u00ean \u0111\u01b0\u1eddng ch\u00e9o $AC$ l\u1ea5y \u0111i\u1ec3m $M$ sao cho $AM= 1\\, cm$. Qua $M$, k\u1ebb c\u00e1c \u0111\u01b0\u1eddng th\u1eb1ng vu\u00f4ng g\u00f3c v\u1edbi c\u00e1c c\u1ea1nh c\u1ee7a h\u00ecnh vu\u00f4ng, ch\u00fang c\u1eaft $AB$ v\u00e0 $CD$ \u1edf $E$ v\u00e0 $F$, c\u1eaft $AD$ v\u00e0 $BC$ \u1edf $G$ v\u00e0 $H$. <br\/> <b> C\u00e2u 1: <\/b> T\u1ee9 gi\u00e1c $AEMG$ l\u00e0 h\u00ecnh g\u00ec? <\/span>","select":["A. H\u00ecnh b\u00ecnh h\u00e0nh","B. H\u00ecnh ch\u1eef nh\u1eadt","C. H\u00ecnh thoi","D. H\u00ecnh vu\u00f4ng"],"explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai12/lv1/img\/H822_D1_6.jpg' \/><\/center> X\u00e9t t\u1ee9 gi\u00e1c $AEMG$, c\u00f3: <br\/> $\\widehat{A}=\\widehat{G}=\\widehat{E}={{90}^{0}}$ (v\u00ec $MG\\bot AD;\\, ME \\bot AB$.)<br\/> $\\Rightarrow AEMG$ l\u00e0 h\u00ecnh ch\u1eef nh\u1eadt (d\u1ea5u hi\u1ec7u nh\u1eadn bi\u1ebft). <br\/> L\u1ea1i c\u00f3: $\\,\\,\\widehat{GAM}=\\widehat{EAM}$ (v\u00ec $AC$ l\u00e0 \u0111\u01b0\u1eddng ch\u00e9o c\u1ee7a h\u00ecnh vu\u00f4ng $ABCD$.)<br\/> $\\Rightarrow $ T\u1ee9 gi\u00e1c $AEGM$ l\u00e0 h\u00ecnh vu\u00f4ng (d\u1ea5u hi\u1ec7u nh\u1eadn bi\u1ebft). <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 D. <\/span> <\/span> ","column":2}]}],"id_ques":1609},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t ","title_trans":"\u0110\u1ec1 chung cho hai c\u00e2u","temp":"multiple_choice","correct":[[1]],"list":[{"point":5,"ques":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai12/lv1/img\/H822_D1_6.jpg' \/><\/center> <br\/> H\u00ecnh vu\u00f4ng $ABCD$ c\u00f3 \u0111\u01b0\u1eddng ch\u00e9o b\u1eb1ng $4 \\,cm$. Tr\u00ean \u0111\u01b0\u1eddng ch\u00e9o $AC$ l\u1ea5y \u0111i\u1ec3m $M$ sao cho $AM= 1\\, cm$. Qua $M$, k\u1ebb c\u00e1c \u0111\u01b0\u1eddng th\u1eb1ng vu\u00f4ng g\u00f3c v\u1edbi c\u00e1c c\u1ea1nh c\u1ee7a h\u00ecnh vu\u00f4ng, ch\u00fang c\u1eaft $AB$ v\u00e0 $CD$ \u1edf $E$ v\u00e0 $F$, c\u1eaft $AD$ v\u00e0 $BC$ \u1edf $G$ v\u00e0 $H$. <br\/> <b> C\u00e2u 2: <\/b> Di\u1ec7n t\u00edch $AEMG$ l\u00e0: <\/span>","select":["A. $0,5\\,cm^2$","B. $1\\,cm^2$","C. $1,5\\,cm^2$","D. $2\\,cm^2$"],"hint":"${{S}_{AEGM}}=\\dfrac{1}{2}EG.AM$.","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai12/lv1/img\/H822_D1_6.jpg' \/><\/center> Theo c\u00e2u 1, ta \u0111\u00e3 ch\u1ee9ng minh \u0111\u01b0\u1ee3c: $AEMG$ l\u00e0 h\u00ecnh vu\u00f4ng <br\/> $\\Rightarrow EG=AM$ <br\/> Ta c\u00f3: $M\\in AC;\\,\\,AM=1\\,cm$ n\u00ean $EG=1\\,cm$ <br\/>${{S}_{AEGM}}=\\dfrac{1}{2}EG.AM$<br\/> $=\\dfrac{1}{2}.1.1=\\dfrac{1}{2}=0,5\\,\\,\\left( c{{m}^{2}} \\right)$ <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 A. <\/span> <br\/> <b> L\u01b0u \u00fd: <\/b> <i> Ta c\u00f3 th\u1ec3 t\u00ednh di\u1ec7n t\u00edch h\u00ecnh vu\u00f4ng theo c\u00f4ng th\u1ee9c t\u00ednh di\u1ec7n t\u00edch h\u00ecnh thoi v\u00ec h\u00ecnh vu\u00f4ng l\u00e0 tr\u01b0\u1eddng h\u1ee3p \u0111\u1eb7c bi\u1ec7t c\u1ee7a h\u00ecnh thoi.<\/i> <\/span> ","column":2}]}],"id_ques":1610}],"lesson":{"save":0,"level":1}}