{"segment":[{"time":9,"part":[{"time":24,"title":"N\u1ed1i c\u00e1c \u00fd \u1edf c\u1ed9t b\u00ean tr\u00e1i v\u1edbi c\u1ed9t b\u00ean ph\u1ea3i \u0111\u1ec3 \u0111\u01b0\u1ee3c c\u00e2u ho\u00e0n ch\u1ec9nh","title_trans":"N\u1ed1i c\u00e1c \u00fd \u1edf c\u1ed9t b\u00ean tr\u00e1i v\u1edbi c\u1ed9t b\u00ean ph\u1ea3i \u0111\u1ec3 \u0111\u01b0\u1ee3c c\u00e2u ho\u00e0n ch\u1ec9nh","audio":"","temp":"matching","correct":[["2","1","3"]],"list":[{"point":5,"image":"https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai6/lv2/img\/9.jpg","left":["$49-x^2y^2$","$3x^2-48y^2$","$9x^2+6xy+6x+4y$"],"right":["$3(x-4y)(x+4y)$","$(7-xy)(7+xy)$","$(3x+2y)(3x+2)$"],"top":100,"hint":"","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/>Ta ph\u00e2n t\u00edch c\u00e1c \u0111a th\u1ee9c \u1edf c\u1ed9t tr\u00e1i th\u00e0nh nh\u00e2n t\u1eed theo ph\u01b0\u01a1ng ph\u00e1p d\u00f9ng h\u1eb1ng \u0111\u1eb3ng th\u1ee9c v\u00e0 \u0111\u1eb7t nh\u00e2n t\u1eed chung:<br\/> $49-{{x}^{2}}{{y}^{2}}={{7}^{2}}-{{\\left( xy \\right)}^{2}}$ <br\/> $3{{x}^{2}}-48{{y}^{2}}=3\\left( {{x}^{2}}-16{{y}^{2}} \\right)$ <br\/> $9{{x}^{2}}+6xy+6x+4y =\\left( 9{{x}^{2}}+6xy \\right)+\\left( 6x+4y \\right)$ <br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/>+ Ta c\u00f3: <br\/> $49-{{x}^{2}}{{y}^{2}} \\\\ ={{7}^{2}}-{{\\left( xy \\right)}^{2}} \\\\ =\\left( 7+xy \\right)\\left( 7-xy \\right)$ <br\/> <br\/> $3{{x}^{2}}-48{{y}^{2}} \\\\ =3\\left( {{x}^{2}}-16{{y}^{2}} \\right) \\\\ =3\\left( x+4y \\right)\\left( x-4y \\right)$ <br\/> <br\/>$\\begin{align} & 9{{x}^{2}}+6xy+6x+4y \\\\ & =\\left( 9{{x}^{2}}+6xy \\right)+\\left( 6x+4y \\right) \\\\ & =3x\\left( 3x+2y \\right)+2\\left( 3x+2y \\right) \\\\ & =\\left( 3x+2y \\right)\\left( 3x+2 \\right) \\\\ \\end{align}$ <span class='basic_pink'> <br\/> K\u1ebft lu\u1eadn: $49-x^2y^2$ n\u1ed1i v\u1edbi $(7-xy)(7+xy)$ <br\/> $3x^2-48y^2$ n\u1ed1i v\u1edbi $3(x-4y)(x+4y)$ <br\/> $9x^2+6xy+6x+4y$ n\u1ed1i v\u1edbi $(3x+2y)(3x+2)$ <\/span> "}]}],"id_ques":551},{"time":9,"part":[{"time":24,"title":"N\u1ed1i c\u00e1c \u00fd \u1edf c\u1ed9t b\u00ean tr\u00e1i v\u1edbi c\u1ed9t b\u00ean ph\u1ea3i \u0111\u1ec3 \u0111\u01b0\u1ee3c c\u00e2u ho\u00e0n ch\u1ec9nh","title_trans":"N\u1ed1i c\u00e1c \u00fd \u1edf c\u1ed9t b\u00ean tr\u00e1i v\u1edbi c\u1ed9t b\u00ean ph\u1ea3i \u0111\u1ec3 \u0111\u01b0\u1ee3c c\u00e2u ho\u00e0n ch\u1ec9nh","audio":"","temp":"matching","correct":[["3","1","2"]],"list":[{"point":5,"image":"{loc]img\/9.jpg","left":["$0,25x(y-1)+0,75y(1-y)$","$x^2-x-y^2-y$","$(x+y)^2-(x-y)^2$"],"right":["$(x+y)(x-y-1)$","$4xy$","$0,25(y-1)(x-3y)$"],"top":100,"hint":"","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/>Ta ph\u00e2n t\u00edch c\u00e1c \u0111a th\u1ee9c \u1edf c\u1ed9t tr\u00e1i th\u00e0nh nh\u00e2n t\u1eed theo ph\u01b0\u01a1ng ph\u00e1p d\u00f9ng h\u1eb1ng \u0111\u1eb3ng th\u1ee9c v\u00e0 \u0111\u1eb7t nh\u00e2n t\u1eed chung<span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/>+ Ta c\u00f3:<br\/> $\\begin{align} & 0,25x(y-1)+0,75y(1-y) \\\\ & =0,25x(y-1)-0,75y(y-1) \\\\ & =(y-1)(0,25x-0,75y) \\\\ & =(y-1).0,25(x-3y) \\\\ & =0,25(y-1)(x-3y) \\\\ \\end{align}$ <br\/> <br\/> $\\begin{align} & {{x}^{2}}-x-{{y}^{2}}-y \\\\ & =({{x}^{2}}-{{y}^{2}})-(x+y) \\\\ & =(x+y)(x-y) - (x+y) \\\\ & =(x+y)(x-y-1) \\\\ \\end{align}$ <br\/> <br\/> $ {{(x+y)}^{2}}-{{(x-y)}^{2}} $<br\/>$ =[(x+y)+(x-y)][(x+y)-(x-y)] $<br\/>$ =2x.2y=4xy $ <br\/> <br\/> <span class='basic_pink'>K\u1ebft lu\u1eadn:<br\/> N\u1ed1i 1 v\u1edbi $0,25(y-1)(x-3y)$<br\/> N\u1ed1i 2 v\u1edbi $(x+y)(x-y-1)$<br\/> N\u1ed1i 3 v\u1edbi $4xy$.<\/span> "}]}],"id_ques":552},{"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":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai6/lv2/img\/13.jpg' \/><\/center> \u0110a th\u1ee9c $y^2(x^2+y)-zx^2-zy$ c\u00f3 m\u1ed9t nh\u00e2n t\u1eed l\u00e0:","select":["A. $y^2-z$ ","B. $y^2+z$ ","C. $x^2-y$","D. $x^2-z$"],"hint":"","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> Nh\u00f3m $y^2(x^2+y)-zx^2-zy$$=y^2(x^2+y)-(zx^2+zy)$ <br\/>Ph\u00e2n t\u00edch \u0111a th\u1ee9c th\u00e0nh nh\u00e2n t\u1eed theo ph\u01b0\u01a1ng ph\u00e1p \u0111\u1eb7t nh\u00e2n t\u1eed chung.<br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/><span class='basic_left'>Ta c\u00f3 :<br\/> $y^2(x^2+y)-zx^2-zy \\\\ =y^2(x^2+y)-(zx^2+zy) \\\\ =y^2(x^2+y)-z(x^2+y) \\\\=(x^2+y)(y^2-z)$. <span><br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 A.<\/span>","column":2}]}],"id_ques":553},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai6/lv2/img\/13.jpg' \/><\/center> \u0110a th\u1ee9c $(x+y)^3-x^3-y^3$ c\u00f3 m\u1ed9t nh\u00e2n t\u1eed l\u00e0:","select":["A. $x+y-1$ ","B. $x-y+1$ ","C. $x+y$","D. $(x+y)^3$"],"hint":"","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> <b> C\u00e1ch 1:<\/b> Nh\u00f3m $(x+y)^3-x^3-y^3$$=(x+y)^3-(x^3+y^3)$<br\/> Khai tri\u1ec3n $(x+y)^3$ v\u00e0 $x^3+y^3$ theo h\u1eb1ng \u0111\u1eb3ng th\u1ee9c, sau \u0111\u00f3 \u0111\u1eb7t nh\u00e2n t\u1eed chung \u0111\u1ec3 ph\u00e2n t\u00edch.<br\/> <b> C\u00e1ch 2:<\/b> <br\/> + <b> B\u01b0\u1edbc 1:<\/b> Khai tri\u1ec3n $(x+y)^3$ theo h\u1eb1ng \u0111\u1eb3ng th\u1ee9c, sau \u0111\u00f3 r\u00fat g\u1ecdn \u0111a th\u1ee9c. <br\/> <b> + B\u01b0\u1edbc 2:<\/b> Ph\u00e2n t\u00edch k\u1ebft qu\u1ea3 $3x^2y+3xy^2$ b\u1eb1ng c\u00e1ch \u0111\u1eb7t nh\u00e2n t\u1eed chung. <br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/><span class='basic_left'><b> C\u00e1ch 1:<\/b> Ta c\u00f3: <br\/>${{\\left( x+y \\right)}^{3}}-{{x}^{3}}-{{y}^{3}} $<br\/>$ ={{\\left( x+y \\right)}^{3}}-\\left( {{x}^{3}}+{{y}^{3}} \\right) $<br\/>$ ={{\\left( x+y \\right)}^{3}}-\\left( x+y \\right)\\left( {{x}^{2}}-xy+{{y}^{2}} \\right) $<br\/>$=\\left( x+y \\right)\\left[ {{\\left( x+y \\right)}^{2}}-\\left( {{x}^{2}}-xy+{{y}^{2}} \\right) \\right] $<br\/>$ =\\left( x+y \\right)\\left[ {{x}^{2}}+2xy+{{y}^{2}}-{{x}^{2}}+xy-{{y}^{2}} \\right] $<br\/>$ =\\left( x+y \\right)3xy$ <br\/> <b> C\u00e1ch 2: <\/b> Ta c\u00f3: <br\/>$\\begin{align} & {{\\left( x+y \\right)}^{3}}-{{x}^{3}}-{{y}^{3}} \\\\ & ={{x}^{3}}+3{{x}^{2}}y+3x{{y}^{2}}+{{y}^{3}}-{{x}^{3}}-{{y}^{3}} \\\\ & =3{{x}^{2}}y+3x{{y}^{2}} \\\\ & =3xy\\left( x+y \\right) \\\\ \\end{align}$ . <span><br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 C.<\/span>","column":2}]}],"id_ques":554},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng trong ph\u00e9p t\u00ednh sau ","title_trans":"","temp":"fill_the_blank","correct":[[["1500"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai6/lv2/img\/12.jpg' \/><\/center> T\u00ednh nhanh. (Kh\u00f4ng s\u1eed d\u1ee5ng m\u00e1y t\u00ednh) <br\/> $15.91,5+150.0,85=$_input_","hint":"","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> Ta t\u00e1ch $15.91,5+150.0,85$$=15.91,5+15.10.0,85$<br\/>Ta \u0111\u1eb7t nh\u00e2n t\u1eed chung $15.91,5+15.10.0,85=15(91,5+8,5)$<br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/> Ta c\u00f3: <br\/>$15.91,5+150.0,85 \\\\ =15.91,5+15.10.0,85 \\\\ =15.91,5+15.8,5 \\\\ =15(91,5+8,5) \\\\ =15.100=1500$ <br\/> <span class='basic_pink'> Do \u0111\u00f3 ph\u1ea3i \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $1500$. <\/span><\/span> "}]}],"id_ques":555},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng trong ph\u00e9p t\u00ednh sau ","title_trans":"","temp":"fill_the_blank","correct":[[["1580"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai6/lv2/img\/12.jpg' \/><\/center> T\u00ednh nhanh. (Kh\u00f4ng s\u1eed d\u1ee5ng m\u00e1y t\u00ednh) <br\/> $15,8.35+15,8.65=$_input_","hint":"","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> Ta \u0111\u1eb7t nh\u00e2n t\u1eed chung $15,8.35+15,8.65=15,8(35+65)$<br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/> Ta c\u00f3: <br\/>$15,8.35+15,8.65 \\\\ =15,8(35+65) \\\\ =15,8.100 \\\\ =1580$ . <br\/> <span class='basic_pink'> Do \u0111\u00f3 ph\u1ea3i \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $1580$. <\/span><\/span> "}]}],"id_ques":556},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t.<br\/> Kh\u1eb3ng \u0111\u1ecbnh d\u01b0\u1edbi \u0111\u00e2y \u0111\u00fang hay sai","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":5,"ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai6/lv2/img\/11.jpg' \/><\/center> Bi\u1ec3u th\u1ee9c $(4n-3)^2-(3n-4)^2$ lu\u00f4n chia h\u1ebft cho $7$ v\u1edbi m\u1ecdi $n\\in \\mathbb{Z}$ ","select":["\u0110\u00fang","Sai"],"hint":"","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> <b> B\u01b0\u1edbc 1: <\/b> Ph\u00e2n t\u00edch $(4n-3)^2-(3n-4)^2$ th\u00e0nh nh\u00e2n t\u1eed theo ph\u01b0\u01a1ng ph\u00e1p d\u00f9ng h\u1eb1ng \u0111\u1eb3ng th\u1ee9c hi\u1ec7u hai b\u00ecnh ph\u01b0\u01a1ng.<br\/> <b> B\u01b0\u1edbc 2:<\/b> N\u1ebfu k\u1ebft qu\u1ea3 thu g\u1ecdn c\u00f3 ch\u1ee9a nh\u00e2n t\u1eed chia h\u1ebft cho $7$ th\u00ec \u0111\u00fang v\u00e0 ng\u01b0\u1ee3c l\u1ea1i l\u00e0 sai. <br\/> <span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/><span class='basic_left'> Ta c\u00f3: <br\/>$ {{(4n-3)}^{2}}-{{(3n-4)}^{2}} $<br\/>$ =\\left[ \\left( 4n-3 \\right)-(3n-4) \\right] \\left[ \\left( 4n-3 \\right)+(3n-4) \\right] $<br\/>$ =(n+1).\\left( 7n-7 \\right) $<br\/>$ =(n+1).7\\left( n-1 \\right)$<br\/>$ =7\\left( n+1 \\right)(n-1) $<br\/>$ \\text{Do}\\,\\,\\,7\\,\\,\\vdots\\,\\,7\\,\\, \\Rightarrow 7\\left( n+1 \\right)(n-1)\\,\\,\\,\\vdots \\,\\,\\,7 \\,\\, \\text{v\u1edbi m\u1ecdi } n\\in \\mathbb{Z}$. <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 \u0110\u00fang.<\/span>","column":2}]}],"id_ques":557},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t.<br\/> Kh\u1eb3ng \u0111\u1ecbnh d\u01b0\u1edbi \u0111\u00e2y \u0111\u00fang hay sai","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":5,"ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai6/lv2/img\/10.jpg' \/><\/center> Hi\u1ec7u c\u00e1c b\u00ecnh ph\u01b0\u01a1ng c\u1ee7a hai s\u1ed1 l\u1ebb li\u00ean ti\u1ebfp lu\u00f4n chia h\u1ebft cho $8$ ","select":["\u0110\u00fang","Sai"],"hint":"","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> <b> B\u01b0\u1edbc 1: <\/b> G\u1ecdi d\u1ea1ng t\u1ed5ng qu\u00e1t c\u1ee7a hai s\u1ed1 l\u1ebb li\u00ean ti\u1ebfp l\u00e0: $2n+1$ v\u00e0 $2n+3$<br\/> <b> B\u01b0\u1edbc 2: <\/b> Hi\u1ec7u c\u00e1c b\u00ecnh ph\u01b0\u01a1ng c\u1ee7a hai s\u1ed1 l\u1ebb li\u00ean ti\u1ebfp l\u00e0: $(2n+3)^2-(2n+1)^2$ .<br\/> <b> B\u01b0\u1edbc 3:<\/b> Ph\u00e2n t\u00edch $(2n+3)^2-(2n+1)^2$ th\u00e0nh nh\u00e2n t\u1eed theo ph\u01b0\u01a1ng ph\u00e1p d\u00f9ng h\u1eb1ng \u0111\u1eb3ng th\u1ee9c hi\u1ec7u hai b\u00ecnh ph\u01b0\u01a1ng.<br\/> <b> B\u01b0\u1edbc 4:<\/b> N\u1ebfu k\u1ebft qu\u1ea3 thu g\u1ecdn c\u00f3 ch\u1ee9a nh\u00e2n t\u1eed chia h\u1ebft cho 8 th\u00ec \u0111\u00fang v\u00e0 ng\u01b0\u1ee3c l\u1ea1i l\u00e0 sai. <br\/> <span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/><span class='basic_left'> G\u1ecdi d\u1ea1ng t\u1ed5ng qu\u00e1t c\u1ee7a hai s\u1ed1 l\u1ebb li\u00ean ti\u1ebfp l\u00e0: $2n+1$ v\u00e0 $2n+3$<br\/> Ta c\u00f3: <br\/>$ {{(2n+3)}^{2}}-{{(2n+1)}^{2}} $<br\/>$ =\\left[ \\left( 2n+3 \\right)-\\left( 2n+1 \\right) \\right]\\left[ \\left( 2n+3 \\right)+\\left( 2n+1 \\right) \\right] $<br\/>$ =2.\\left( 4n+4 \\right) $<br\/>$ =2.4\\left( n+1 \\right) $<br\/>$ =8\\left( n+1 \\right) $<br\/>$ \\text{Do}\\,\\,\\,8\\,\\,\\vdots\\,\\,8\\,\\, \\Rightarrow 8\\left( n+1 \\right)\\,\\,\\,\\vdots \\,\\,\\,8 $. <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 \u0110\u00fang.<\/span>","column":2}]}],"id_ques":558},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng ","title_trans":"","temp":"fill_the_blank","correct":[[["-42"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai6/lv2/img\/9.jpg' \/><\/center> Ph\u00e2n t\u00edch \u0111a th\u1ee9c $a^3-b^3+2b-2a$ th\u00e0nh nh\u00e2n t\u1eed r\u1ed3i t\u00ednh gi\u00e1 tr\u1ecb bi\u1ec3u th\u1ee9c t\u1ea1i $a = -3; b = 3$. <br\/> \u0110\u00e1p \u00e1n l\u00e0: _input_","hint":"","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> <b> B\u01b0\u1edbc 1: <\/b> Ta nh\u00f3m: $a^3-b^3+2b-2a$$=(a^3-b^3)+(2b-2a)$ <br\/> <b>B\u01b0\u1edbc 2:<\/b> Ph\u00e2n t\u00edch $(a^3-b^3)+(2b-2a)$ th\u00e0nh nh\u00e2n t\u1eed b\u1eb1ng ph\u01b0\u01a1ng ph\u00e1p d\u00f9ng h\u1eb1ng \u0111\u1eb3ng th\u1ee9c v\u00e0 \u0111\u1eb7t nh\u00e2n t\u1eed chung.<br\/> <b>B\u01b0\u1edbc 3:<\/b> Thay $a = -3; b = 3$ v\u00e0o bi\u1ec3u th\u1ee9c \u0111\u1ec3 t\u00ednh gi\u00e1 tr\u1ecb.<br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/> Ta c\u00f3: <br\/>$a^3-b^3+2b-2a \\\\ =(a^3-b^3)+(2b-2a) \\\\ =(a-b)(a^2+ab+b^2)+2(b-a) \\\\ =(a-b)(a^2+ab+b^2)-2(a-b) \\\\ =(a-b)(a^2+ab+b^2-2)$ <br\/>Thay $a = -3; b = 3$ v\u00e0o bi\u1ec3u th\u1ee9c sau khi thu g\u1ecdn, ta \u0111\u01b0\u1ee3c:<br\/>$(a-b)(a^2+ab+b^2-2)=(-3-3)[(-3)^2+(-3).3+3^2-2]=(-6).7=-42$ . <br\/> <span class='basic_pink'> Do \u0111\u00f3 s\u1ed1 ph\u1ea3i \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $-42$. <\/span><\/span> "}]}],"id_ques":559},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng ","title_trans":"","temp":"fill_the_blank","correct":[[["-9"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai6/lv2/img\/8.jpg' \/><\/center> Ph\u00e2n t\u00edch \u0111a th\u1ee9c $x^3+2x^2y+xy^2-4x$ th\u00e0nh nh\u00e2n t\u1eed r\u1ed3i t\u00ednh gi\u00e1 tr\u1ecb c\u1ee7a bi\u1ec3u th\u1ee9c t\u1ea1i $x = 3; y = -2$. <br\/> \u0110\u00e1p \u00e1n l\u00e0: _input_","hint":"","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> <b> B\u01b0\u1edbc 1: <\/b> Ta c\u00f3: $x^3+2x^2y+xy^2-4x=x\\left[ (x+y)^2-4 \\right]$ <br\/> <b>B\u01b0\u1edbc 2:<\/b> Ph\u00e2n t\u00edch $(x+y)^2-4$ th\u00e0nh nh\u00e2n t\u1eed b\u1eb1ng ph\u01b0\u01a1ng ph\u00e1p d\u00f9ng h\u1eb1ng \u0111\u1eb3ng th\u1ee9c th\u1ee9 ba.<br\/> <b>B\u01b0\u1edbc 3:<\/b> Thay $x = 3; y = -2$ v\u00e0o bi\u1ec3u th\u1ee9c \u0111\u1ec3 t\u00ednh gi\u00e1 tr\u1ecb.<br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/> Ta c\u00f3: <br\/> $\\begin{align} & {{x}^{3}}+2{{x}^{2}}y+x{{y}^{2}}-4x \\\\ & =x\\left( {{x}^{2}}+2xy+{{y}^{2}}-4 \\right) \\\\ & =x\\left[ {{\\left( x+y \\right)}^{2}}-4 \\right] \\\\ & =x\\left( x+y-2 \\right)\\left( x+y+2 \\right) \\\\ \\end{align}$ <br\/>Thay x = 3; y = -2 v\u00e0o bi\u1ec3u th\u1ee9c \u0111\u00e3 thu g\u1ecdn, ta \u0111\u01b0\u1ee3c:<br\/>$\\begin{align}& x\\left( x+y+2 \\right)\\left( x+y-2 \\right) \\\\ & =3.\\left( 3-2+2 \\right)\\left( 3-2-2 \\right) \\\\ & =3.3.\\left( -1 \\right) \\\\ & =-9 \\\\ \\end{align}$ <br\/> <span class='basic_pink'> Do \u0111\u00f3 s\u1ed1 ph\u1ea3i \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $-9$ <\/span><\/span> "}]}],"id_ques":560},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng ","title_trans":"","temp":"fill_the_blank","correct":[[["25"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai6/lv2/img\/5.jpg' \/><\/center> Gi\u00e1 tr\u1ecb c\u1ee7a bi\u1ec3u th\u1ee9c $-16yz^2-24y^2z-9y^3$ v\u1edbi $y = - 1; z = 2$ l\u00e0 _input_","hint":"","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> <b> B\u01b0\u1edbc 1: <\/b> \u0110\u1eb7t nh\u00e2n t\u1eed chung <br\/> <b>B\u01b0\u1edbc 2:<\/b> D\u00f9ng h\u1eb1ng \u0111\u1eb3ng th\u1ee9c \u0111\u1ec3 ph\u00e2n t\u00edch ti\u1ebfp.<br\/> <b>B\u01b0\u1edbc 3:<\/b> Thay $y = - 1; z = 2$ v\u00e0o bi\u1ec3u th\u1ee9c \u0111\u1ec3 t\u00ednh gi\u00e1 tr\u1ecb.<br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/> Ta c\u00f3: <br\/> $\\begin{align} & -16y{{z}^{2}}-24{{y}^{2}}z-9{{y}^{3}} \\\\ & =-y\\left( 16{{z}^{2}}+24yz+9{{y}^{2}} \\right) \\\\ & =-y{{\\left( 4z+3y \\right)}^{2}} \\\\ \\end{align}$ <br\/>Thay $y = - 1; z = 2$ v\u00e0o bi\u1ec3u th\u1ee9c sau khi thu g\u1ecdn, ta \u0111\u01b0\u1ee3c:<br\/>$-(-1).{{\\left( 4.2+3.(-1) \\right)}^{2}}={{5}^{2}}=25$ <br\/> <span class='basic_pink'> Do \u0111\u00f3 s\u1ed1 ph\u1ea3i \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $25$. <\/span><\/span> "}]}],"id_ques":561},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng ","title_trans":"","temp":"fill_the_blank_random","correct":[[["-4"],["0"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai6/lv2/img\/4.jpg' \/><\/center> Bi\u1ebft $4-x^2-4x-4=0$, khi \u0111\u00f3 $\\left[ \\begin{align} & x= \\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}\\\\ & x=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{} \\\\ \\end{align} \\right.$ ","hint":"","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> <b> B\u01b0\u1edbc 1:<\/b> Nh\u00f3m $4-x^2-4x-4=4-(x^2+4x+4) =2^2-(x+2)^2$ <br\/><b>B\u01b0\u1edbc 2:<\/b> Ph\u00e2n t\u00edch $2^2-(x+2)^2$ th\u00e0nh nh\u00e2n t\u1eed theo ph\u01b0\u01a1ng ph\u00e1p d\u00f9ng h\u1eb1ng \u0111\u1eb3ng th\u1ee9c hi\u1ec7u hai b\u00ecnh ph\u01b0\u01a1ng.<br\/> <b> B\u01b0\u1edbc 2:<\/b> N\u1ebfu $a.b = 0$ th\u00ec $a = 0$ ho\u1eb7c $b = 0$. <br\/><span class='basic_green'>B\u00e0i gi\u1ea3i<\/span><br\/> Ta c\u00f3:<br\/> $\\begin{aligned} & 4-{{x}^{2}}-4x-4=0 \\\\ &\\Leftrightarrow 4-\\left( {{x}^{2}}+4x+4 \\right)=0 \\\\ &\\Leftrightarrow 4-{{\\left( x+2 \\right)}^{2}}=0 \\\\ &\\Leftrightarrow \\left[ 2+\\left( x+2 \\right) \\right]\\left[ 2-\\left( x+2 \\right) \\right]=0 \\\\ &\\Leftrightarrow \\left( x+4 \\right)\\left( -x \\right)=0 \\\\ & \\Leftrightarrow \\left[ \\begin{aligned} & x+4=0 \\\\ & -x=0 \\\\ \\end{aligned} \\right.\\Leftrightarrow \\left[ \\begin{aligned} & x=-4 \\\\ & x=0 \\\\ \\end{aligned} \\right. \\\\ \\end{aligned}$ <br\/> <span class='basic_pink'> Do \u0111\u00f3 c\u00e1c s\u1ed1 ph\u1ea3i \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $0$ v\u00e0 $- 4$. <\/span><\/span> "}]}],"id_ques":562},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng ","title_trans":"","temp":"fill_the_blank","correct":[[["5"],["3"],["-1"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai6/lv2/img\/3.jpg' \/><\/center> Bi\u1ebft $2x\\left( 3x-5 \\right)=10-6x$, khi \u0111\u00f3 $\\left[ \\begin{align} & x= \\dfrac{\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}}{\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}}\\\\ & x=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{} \\\\ \\end{align} \\right.$ ","hint":"<b> B\u01b0\u1edbc 1: <\/b> Chuy\u1ec3n c\u00e1c h\u1ea1ng t\u1eed t\u1eeb v\u1ebf ph\u1ea3i sang v\u1ebf tr\u00e1i.<br\/><b>B\u01b0\u1edbc 2:<\/b> Ph\u00e2n t\u00edch v\u1ebf tr\u00e1i th\u00e0nh nh\u00e2n t\u1eed","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> <b> B\u01b0\u1edbc 1: <\/b> Chuy\u1ec3n c\u00e1c h\u1ea1ng t\u1eed t\u1eeb v\u1ebf ph\u1ea3i sang v\u1ebf tr\u00e1i.<br\/> <b>B\u01b0\u1edbc 2:<\/b> Ph\u00e2n t\u00edch v\u1ebf tr\u00e1i th\u00e0nh nh\u00e2n t\u1eed $2x\\left( 3x-5 \\right)-\\left( 10-6x \\right)$$=2x(x+1)(3x-5)$ theo ph\u01b0\u01a1ng ph\u00e1p \u0111\u1eb7t nh\u00e2n t\u1eed chung.<br\/> <b> B\u01b0\u1edbc 3:<\/b> N\u1ebfu $a.b = 0$ th\u00ec $a = 0$ ho\u1eb7c $b = 0$. <br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/> Ta c\u00f3:<br\/> $\\begin{aligned} & 2x\\left( 3x-5 \\right)=10-6x \\\\ &\\Leftrightarrow 2x\\left( 3x-5 \\right)-\\left( 10-6x \\right)=0 \\\\ &\\Leftrightarrow 2x\\left( 3x-5 \\right)-2\\left( 5-3x \\right)=0 \\\\ &\\Leftrightarrow 2x\\left( 3x-5 \\right)+2\\left( 3x-5 \\right)=0 \\\\ &\\Leftrightarrow \\left( 3x-5 \\right)\\left( 2x+2 \\right)=0 \\\\ &\\Leftrightarrow \\left( 3x-5 \\right).2.\\left( x+1 \\right)=0 \\\\ &\\Leftrightarrow 2\\left( x+1 \\right)\\left( 3x-5 \\right)=0 \\\\ &\\Leftrightarrow \\left[ \\begin{aligned} & x+1=0 \\\\ & 3x-5=0 \\\\ \\end{aligned} \\right.\\Leftrightarrow \\left[ \\begin{aligned} & x=-1 \\\\ & x=\\dfrac{5}{3} \\\\ \\end{aligned} \\right. \\\\ \\end{aligned}$ <br\/> <span class='basic_pink'> Do \u0111\u00f3 c\u00e1c s\u1ed1 ph\u1ea3i \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $\\dfrac{5}{3}$ v\u00e0 $-1$. <\/span><\/span> "}]}],"id_ques":563},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng ","title_trans":"","temp":"fill_the_blank_random","correct":[[["0"],["-3"],["3"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai6/lv2/img\/16.jpg' \/><\/center> Bi\u1ebft $4x^3-36x=0$, khi \u0111\u00f3 $\\left[ \\begin{align} & x= \\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}\\\\ & x=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{} \\\\ & x=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{} \\\\ \\end{align} \\right.$ ","hint":"","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> <b> B\u01b0\u1edbc 1:<\/b> Ph\u00e2n t\u00edch v\u1ebf tr\u00e1i th\u00e0nh nh\u00e2n t\u1eed $4x(x-3)(x+3)$ <br\/> <b>B\u01b0\u1edbc 2:<\/b> N\u1ebfu $a.b.c = 0$ th\u00ec $a = 0$ ho\u1eb7c $b = 0$ ho\u1eb7c $c = 0$. <br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/> Ta c\u00f3:<br\/> $\\begin{aligned} & 4{{x}^{3}}-36x=0 \\\\ &\\Leftrightarrow 4x\\left( {{x}^{2}}-9 \\right)=0 \\\\ &\\Leftrightarrow 4x\\left( x+3 \\right)\\left( x-3 \\right)=0 \\\\ &\\Leftrightarrow \\left[ \\begin{aligned} & 4x=0 \\\\ & x+3=0 \\\\ & x-3=0 \\\\ \\end{aligned} \\right.\\Leftrightarrow \\left[ \\begin{aligned} & x=0 \\\\ & x=-3 \\\\ & x=3 \\\\ \\end{aligned} \\right. \\\\ \\end{aligned}$ <br\/> <span class='basic_pink'> Do \u0111\u00f3 c\u00e1c s\u1ed1 ph\u1ea3i \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $-3$ v\u00e0 $3$ v\u00e0 $0$. <\/span><\/span> "}]}],"id_ques":564},{"time":24,"part":[{"title":"\u0110i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng trong k\u1ebft qu\u1ea3 ph\u00e2n t\u00edch \u0111a th\u1ee9c th\u00e0nh nh\u00e2n t\u1eed","title_trans":"","temp":"fill_the_blank","correct":[[["x"],["y"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai6/lv2/img\/16.jpg' \/><\/center> $1-\\left( {{x}^{2}}-2xy+{{y}^{2}} \\right)$$=(1- \\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}+\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{})(1+x-y) $","hint":"","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/><b> B\u01b0\u1edbc 1:<\/b> \u0110\u01b0a $1-\\left( {{x}^{2}}-2xy+{{y}^{2}} \\right)$$=1-(x-y)^2$.<br\/> <b> B\u01b0\u1edbc 2:<\/b> S\u1eed d\u1ee5ng h\u1eb1ng \u0111\u1eb3ng th\u1ee9c hi\u1ec7u hai b\u00ecnh ph\u01b0\u01a1ng \u0111\u1ec3 ph\u00e2n t\u00edch th\u00e0nh nh\u00e2n t\u1eed. <br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/><span class='basic_left'>Ta c\u00f3:<br\/> $\\begin{align} & 1-\\left( {{x}^{2}}-2xy+{{y}^{2}} \\right) \\\\ & =1-{{\\left( x-y \\right)}^{2}} \\\\ & =\\left( 1+x-y \\right)\\left( 1-x+y \\right) \\\\ \\end{align}$ <span><br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n c\u1ea7n \u0111i\u1ec1n l\u00e0 $x$ v\u00e0 $y$.<\/span>"}]}],"id_ques":565},{"time":24,"part":[{"title":"Ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":5,"select":["A. $a = 2y; b = \\dfrac{z}{2}$"," B. $a = y; b = \\dfrac{z}{2}$","C. $a = y; b = \\dfrac{-z}{2}$"],"ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai6/lv2/img\/16.jpg' \/><\/center> $8{{y}^{3}}-\\dfrac{1}{8}{{z}^{3}}=(a+ b)\\left( 4{{y}^{2}}+yz+\\dfrac{1}{4}{{z}^{2}} \\right)$<br\/> $a,b = ?$","hint":"","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/>Ph\u00e2n t\u00edch $8{{y}^{3}}-\\dfrac{1}{8}{{z}^{3}}$$=(2y)^3-\\left(\\dfrac{1}{2}z\\right)^3$ th\u00e0nh nh\u00e2n t\u1eed theo ph\u01b0\u01a1ng ph\u00e1p h\u1eb1ng \u0111\u1eb3ng th\u1ee9c<br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/><span class='basic_left'>Ta c\u00f3:<br\/> $8{{y}^{3}}-\\dfrac{1}{8}{{z}^{3}} \\\\ ={{\\left( 2y \\right)}^{3}}-{{\\left( \\dfrac{1}{2}z \\right)}^{3}} \\\\ =\\left( 2y-\\dfrac{1}{2}z \\right)\\left( 4{{y}^{2}}+yz+\\dfrac{1}{4}{{z}^{2}} \\right)$ <span>"}]}],"id_ques":566},{"time":24,"part":[{"title":"\u0110i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng trong k\u1ebft qu\u1ea3 ph\u00e2n t\u00edch \u0111a th\u1ee9c th\u00e0nh nh\u00e2n t\u1eed","title_trans":"","temp":"fill_the_blank","correct":[[["3y"],["2"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai6/lv2/img\/10.jpg' \/><\/center> $3{{y}^{2}}+9yz-2y-6z$$=(\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}-\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{})(y+3z) $","hint":"","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/><b> B\u01b0\u1edbc 1:<\/b> Nh\u00f3m $3{{y}^{2}}+9yz-2y-6z=(3{{y}^{2}}+9yz)-(2y+6z)$<br\/> <b> B\u01b0\u1edbc 2:<\/b> Ph\u00e2n t\u00edch ti\u1ebfp theo ph\u01b0\u01a1ng ph\u00e1p \u0111\u1eb7t nh\u00e2n t\u1eed chung. <br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/><span class='basic_left'>Ta c\u00f3:<br\/> $\\begin{align} & 3{{y}^{2}}+9yz-2y-6z \\\\ & =\\left( 3{{y}^{2}}+9yz \\right)-\\left( 2y+6z \\right) \\\\ & =3y\\left( y+3z \\right)-2\\left( y+3z \\right) \\\\ & =\\left( y+3z \\right)\\left( 3y-2 \\right) \\\\ \\end{align}$ <span><br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n c\u1ea7n \u0111i\u1ec1n l\u00e0 $3y$ v\u00e0 $2$.<\/span>"}]}],"id_ques":567},{"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":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai6/lv2/img\/11.jpg' \/><\/center> Ph\u00e2n t\u00edch \u0111a th\u1ee9c ${{x}^{4}}+2{{x}^{2}}y+{{y}^{2}}$ th\u00e0nh nh\u00e2n t\u1eed, ta \u0111\u01b0\u1ee3c:","select":["A. $(x+y)^2$ ","B. $(x-y)^2$ ","C. $(x^2+y)^2$","D. $(x^2-y)^2$"],"hint":"","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/>\u0110\u01b0a ${{x}^{4}}+2{{x}^{2}}y+{{y}^{2}}$ v\u1ec1 b\u00ecnh ph\u01b0\u01a1ng c\u1ee7a m\u1ed9t t\u1ed5ng. <br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/><span class='basic_left'>Ta c\u00f3:<br\/> $\\begin{align} & {{x}^{4}}+2{{x}^{2}}y+{{y}^{2}} \\\\ & ={{\\left( {{x}^{2}} \\right)}^{2}}+2{{x}^{2}}y+{{y}^{2}} \\\\ & ={{\\left( {{x}^{2}}+y \\right)}^{2}} \\\\ \\end{align}$<span><br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 C.<\/span>","column":2}]}],"id_ques":568},{"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":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai6/lv2/img\/9.jpg' \/><\/center> Ph\u00e2n t\u00edch \u0111a th\u1ee9c $\\left( 8{{a}^{3}}-27{{b}^{3}} \\right)-2a\\left( 4{{a}^{2}}-9{{b}^{2}} \\right)$ th\u00e0nh nh\u00e2n t\u1eed, ta \u0111\u01b0\u1ee3c:","select":["A. $9b^2(a-b)$ ","B. $9b^2(2a-3b)$ ","C. $18b^2(a-b)$","D. $b^2(2a-3b)$"],"hint":"","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/><b>B\u01b0\u1edbc 1:<\/b> Ph\u00e2n t\u00edch theo ph\u01b0\u01a1ng ph\u00e1p d\u00f9ng h\u1eb1ng \u0111\u1eb3ng th\u1ee9c:<br\/> $a^2-b^2=(a+b)(a-b)$<br\/>$a^3-b^3=(a-b)(a^2+ab+b^2)$ <br\/> <b> B\u01b0\u1edbc 2: <\/b>\u0110\u1eb7t nh\u00e2n t\u1eed chung \u0111\u1ec3 ph\u00e2n t\u00edch ti\u1ebfp. <br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/>Ta c\u00f3:<br\/> $ \\left( 8{{a}^{3}}-27{{b}^{3}} \\right) -2a\\left( 4{{a}^{2}}-9{{b}^{2}} \\right) $<br\/>$ =\\left[ {{\\left( 2a \\right)}^{3}}-{{\\left( 3b \\right)}^{3}} \\right]-2a\\left[ {{\\left( 2a \\right)}^{2}}-{{\\left( 3b \\right)}^{2}} \\right] $<br\/>$ =\\left[ \\left( 2a-3b \\right)\\left( 4{{a}^{2}}+6ab+9{{b}^{2}} \\right) \\right]-2a\\left[ \\left( 2a+3b \\right)\\left( 2a-3b \\right) \\right] $<br\/>$ =\\left( 2a-3b \\right)\\left[ \\left( 4{{a}^{2}}+6ab+9{{b}^{2}} \\right)-2a\\left( 2a+3b \\right) \\right] $<br\/>$ =\\left( 2a-3b \\right)\\left( 4{{a}^{2}}+6ab+9{{b}^{2}}-4{{a}^{2}}-6ab \\right) $<br\/>$ =\\left( 2a-3b \\right).9{{b}^{2}} $<span><br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 B.<\/span>","column":2}]}],"id_ques":569},{"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":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai6/lv2/img\/8.jpg' \/><\/center> Ph\u00e2n t\u00edch \u0111a th\u1ee9c ${{\\left( 2a+b \\right)}^{2}}-{{\\left( 2b+a \\right)}^{2}}$ th\u00e0nh nh\u00e2n t\u1eed, ta \u0111\u01b0\u1ee3c:","select":["A. $3(a+b)(a-b)$ ","B. $(a+b)(a-b)$ ","C. $(4a-b)(4a+b)$","D. $2(a+b)(a-b)$"],"hint":"","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/>Ph\u00e2n t\u00edch th\u00e0nh nh\u00e2n t\u1eed theo ph\u01b0\u01a1ng ph\u00e1p d\u00f9ng h\u1eb1ng \u0111\u1eb3ng th\u1ee9c: $a^2-b^2=(a+b)(a-b)$. <br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/><span class='basic_left'>Ta c\u00f3:<br\/> $ {{\\left( 2a+b \\right)}^{2}}-{{\\left( 2b+a \\right)}^{2}} $<br\/>$ =\\left[ \\left( 2a+b \\right)+\\left( 2b+a \\right) \\right]\\left[ \\left( 2a+b \\right)-\\left( 2b+a \\right) \\right] $<br\/>$=( 3a+3b )( a-b )$<br\/>$ =3\\left( a+b \\right)\\left( a-b \\right) $<span><br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 A.<\/span>","column":2}]}],"id_ques":570}],"lesson":{"save":0,"level":2}}