{"segment":[{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":10,"ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai2/lv3/img\/1.png' \/><\/center>\u0110a th\u1ee9c $f\\left( x \\right)=\\left( x-1 \\right)\\left( x+2 \\right)-\\left( x-3 \\right)$ v\u00f4 nghi\u1ec7m. \u0110\u00fang hay sai?","select":["\u0110\u00fang","Sai"],"hint":"Nghi\u1ec7m c\u1ee7a $f(x)$ l\u00e0 c\u00e1c gi\u00e1 tr\u1ecb c\u1ee7a $x$ th\u1ecfa m\u00e3n $f(x) = 0$. <br\/> N\u1ebfu kh\u00f4ng t\u00ecm \u0111\u01b0\u1ee3c $x$ th\u00ec f(x) v\u00f4 nghi\u1ec7m v\u1edbi m\u1ecdi $x$.","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> <b>B\u01b0\u1edbc 1:<\/b> Cho $f(x) = 0$.<br\/> <b>B\u01b0\u1edbc 2:<\/b> Bi\u1ebfn \u0111\u1ed5i, r\u00fat g\u1ecdn t\u1eebng b\u01b0\u1edbc \u0111\u1ec3 t\u00ecm $x$. <br\/><span class='basic_green'>B\u00e0i gi\u1ea3i<\/span><br\/>Ta c\u00f3: <br\/>$\\begin{align} &\\left( x \\right)=0 \\\\& \\Leftrightarrow \\left( x-1 \\right)\\left( x+2 \\right)-\\left( x-3 \\right)=0 \\\\ & \\Leftrightarrow {{x}^{2}}+2x-x-2-x+3 =0 \\\\ & \\Leftrightarrow {{x}^{2}}+1 =0 \\\\ &\\end{align}$<br\/> Do $x^2 \\ge 0 \\Rightarrow x^2+1 \\ge 1$ v\u1edbi m\u1ecdi $x$.<br\/> Do \u0111\u00f3 f(x) v\u00f4 nghi\u1ec7m v\u1edbi m\u1ecdi $x$.<br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 \u0110\u00fang.<\/span>","column":2}]}],"id_ques":371},{"time":24,"part":[{"time":3,"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":[["1","2"]],"list":[{"point":10,"left":["$A={{x}^{7}}-80{{x}^{6}}+80{{x}^{5}} \\\\-80{{x}^{4}}+80x^3$","$B=2{{x}^{10}}-15{{x}^{9}}+15{{x}^{8}}-....\\\\-15x+15$"],"right":["T\u1ea1i $x = 1$ th\u00ec gi\u00e1 tr\u1ecb bi\u1ec3u th\u1ee9c b\u1eb1ng $1$","T\u1ea1i $x = 1$ th\u00ec gi\u00e1 tr\u1ecb bi\u1ec3u th\u1ee9c b\u1eb1ng $2$"],"top":100,"hint":"Thay $x = 1$ v\u00e0o A v\u00e0 B \u0111\u1ec3 t\u00ednh gi\u00e1 tr\u1ecb c\u1ee7a A v\u00e0 B.","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> <b>B\u01b0\u1edbc 1:<\/b> Thay $x = 1$ v\u00e0o $A$ v\u00e0 $B$ \u0111\u1ec3 t\u00ednh gi\u00e1 tr\u1ecb c\u1ee7a $A$ v\u00e0 $B$.<br\/> <b>B\u01b0\u1edbc 2:<\/b> N\u1ed1i c\u1ed9t tr\u00e1i v\u1edbi c\u1ed9t ph\u1ea3i t\u01b0\u01a1ng \u1ee9ng. <br\/><br\/><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/> Thay $x = 1$ v\u00e0o $A$, ta \u0111\u01b0\u1ee3c:<br\/> $A={{x}^{7}}-80{{x}^{6}}+80{{x}^{5}}-80{{x}^{4}}+80x^3$<br\/>$=1^7-80.1^6+80.1^5-80.1^4+80.1^3$<br\/>$=1$<br\/> Thay $x = 1$ v\u00e0o $B$, ta \u0111\u01b0\u1ee3c:<br\/>$B=2{{x}^{10}}-15{{x}^{9}}+15{{x}^{8}}-....-15x+15$<br\/>$=2.1^{10}-15.1^9+15.1^8-...+15.1+15$<br\/>$= 2 - 15 + 15 - 15 + ...- 15 + 15$<br\/>$= 2-(- 15 + 15) + (-15 + 15) + ...+ (-15 + 15)$<br\/>$= 2 + 0 + ... + 0$<br\/>$=2$ <\/span> <\/span> <br\/>"}]}],"id_ques":372},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":10,"ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai2/lv3/img\/1.png' \/><\/center>Bi\u1ec3u th\u1ee9c $\\left( 2m-3 \\right)\\left( 3n-2 \\right)$$-\\left( 3m-2 \\right)\\left( 2n-3 \\right)$ lu\u00f4n chia h\u1ebft cho $5$ v\u1edbi m\u1ecdi $m, n$ $\\in\\mathbb{Z}$. \u0110\u00fang hay sai? ","select":["\u0110\u00fang","Sai"],"hint":"","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn<\/span><br\/> <b>B\u01b0\u1edbc 1:<\/b> Ta bi\u1ebfn \u0111\u1ed5i v\u00e0 r\u00fat g\u1ecdn bi\u1ec3u th\u1ee9c, s\u1eed d\u1ee5ng c\u00f4ng th\u1ee9c: $a(b+c)=a.b+a.c$ v\u00e0 $(a+b)(c+d)=ac+ad+bc+bd$ <br\/> <b>B\u01b0\u1edbc 2:<\/b> Nh\u1eadn \u0111\u1ecbnh k\u1ebft qu\u1ea3 \u0111\u00e3 r\u00fat g\u1ecdn xem c\u00f3 ch\u1ee9a th\u1eeba s\u1ed1 chia h\u1ebft cho $5$ kh\u00f4ng.<br\/> + N\u1ebfu c\u00f3 ch\u1ee9a th\u1eeba s\u1ed1 chia h\u1ebft cho $5$ th\u00ec bi\u1ec3u th\u1ee9c \u0111\u00e3 cho chia h\u1ebft cho $5$.<br\/>+ N\u1ebfu kh\u00f4ng ch\u1ee9a th\u1eeba s\u1ed1 chia h\u1ebft cho $5$ th\u00ec bi\u1ec3u th\u1ee9c \u0111\u00e3 cho kh\u00f4ng chia h\u1ebft cho $5$. <br\/><span class='basic_green'>B\u00e0i gi\u1ea3i<\/span><br\/><span class='basic_left'>Ta c\u00f3:<br\/>$ \\left( 2m-3 \\right)\\left( 3n-2 \\right)$$-\\left( 3m-2 \\right)\\left( 2n-3 \\right) $<br\/>$ =6mn-4m-9n+6-6mn+9m+4n-6 $<br\/>$ =5m-5n $<br\/>$ =5\\left( m-n \\right) $<br\/> Do $5\\vdots 5 \\Rightarrow 5(m-n) \\vdots 5$ v\u1edbi m\u1ecdi m, n $\\in \\mathbb{Z}$<span><br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 \u0110\u00fang.<\/span>","column":2}]}],"id_ques":373},{"time":24,"part":[{"title":"\u0110i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng ","title_trans":"","temp":"fill_the_blank","correct":[[["-2"],["3"]]],"list":[{"point":10,"width":40,"type_input":"","ques":"Bi\u1ebft $\\left( x-3 \\right)\\left( 2{{x}^{2}}+a\\,x+b \\right)$$=2{{x}^{3}}-8{{x}^{2}}+9x-9$. <br\/> Khi \u0111\u00f3 $\\left\\{ \\begin{align} & a=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{} \\\\ & b=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{} \\\\ \\end{align} \\right.$","hint":"Bi\u1ebfn \u0111\u1ed5i v\u1ebf tr\u00e1i. \u0110\u1ed3ng nh\u1ea5t h\u1ec7 s\u1ed1 v\u1ebf tr\u00e1i v\u1edbi v\u1ebf ph\u1ea3i \u0111\u1ec3 t\u00ecm $a, b$.","explain":"<span class='basic_left'>Ta c\u00f3: <br\/>$ \\left( x-3 \\right)\\left( 2{{x}^{2}}+a\\,x+b \\right) $ $=2{{x}^{3}}-8{{x}^{2}}+9x-9 $<br\/>$\\Leftrightarrow$ $ 2{{x}^{3}}+a\\,{{x}^{2}}+bx-6{{x}^{2}}-3ax-3b$ $=2{{x}^{3}}-8{{x}^{2}}+9x-9 $<br\/>$\\Leftrightarrow$ $ 2{{x}^{3}}+\\left( a-6 \\right){{x}^{2}}+\\left( b-3a \\right)x-3b$ $=2{{x}^{3}}-8{{x}^{2}}+9x-9 $<br\/>\u0110\u1ed3ng nh\u1ea5t h\u1ec7 s\u1ed1 v\u1ebf tr\u00e1i v\u1edbi v\u1ebf ph\u1ea3i ta c\u00f3: <br\/> $\\left\\{ \\begin{aligned} & a-6=-8 \\\\ & b-3a=9 \\\\ & -3b=-9 \\\\ \\end{aligned} \\right.\\Rightarrow \\left\\{ \\begin{aligned} & a=-2 \\\\ & b+6=9 \\\\ & b=3 \\\\ \\end{aligned} \\right.$$\\Rightarrow \\left\\{ \\begin{aligned} & a=-2 \\\\ & b=3 \\\\ \\end{aligned} \\right.$ <br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n c\u1ea7n \u0111i\u1ec1n l\u00e0 $a = - 2; b = 3.$ <\/span><\/span> "}]}],"id_ques":374},{"time":24,"part":[{"title":"\u0110i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng ","title_trans":"","temp":"fill_the_blank","correct":[[["-140"]]],"list":[{"point":10,"width":40,"type_input":"","ques":"Gi\u00e1 tr\u1ecb c\u1ee7a bi\u1ec3u th\u1ee9c $A=\\left( -5x+4 \\right)\\left( 3x-2 \\right)$$+\\left( -2x+3 \\right)\\left( x-2 \\right)$ t\u1ea1i $x=-2$ l\u00e0 _input_","hint":"R\u00fat g\u1ecdn bi\u1ec3u th\u1ee9c $A$ sau \u0111\u00f3 thay gi\u00e1 tr\u1ecb $x$ v\u00e0o bi\u1ec3u th\u1ee9c $A$ \u0111\u00e3 cho \u0111\u1ec3 t\u00ednh.","explain":"<span class='basic_left'>Ta r\u00fat g\u1ecdn bi\u1ec3u th\u1ee9c \u0111\u00e3 cho:<br\/>$ A=\\left( -5x+4 \\right)\\left( 3x-2 \\right)$$+\\left( -2x+3 \\right)\\left( x-2 \\right) $<br\/>$ =-15{{x}^{2}}+10x+12x-8-2{{x}^{2}}+4x+3x-6 $<br\/>$ =-17{{x}^{2}}+29x-14 $<br\/>Thay $x = -2$ v\u00e0o $A$, ta \u0111\u01b0\u1ee3c: <br\/>$\\begin{align} & A=-17{{x}^{2}}+29x-14 \\\\ & =-17.{{\\left( -2 \\right)}^{2}}+29.\\left( -2 \\right)-14 \\\\ & =-68-58-14 \\\\ & =-140 \\\\ \\end{align}$ <br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n c\u1ea7n \u0111i\u1ec1n l\u00e0 $- 140$. <\/span><\/span> "}]}],"id_ques":375},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":10,"ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai2/lv3/img\/1.png' \/><\/center>Gi\u00e1 tr\u1ecb c\u1ee7a bi\u1ec3u th\u1ee9c $P=\\left( 5x-2 \\right)\\left( x+1 \\right)$$-\\left( x-3 \\right)\\left( 5x+1 \\right)-17\\left( x-2 \\right)$ <br\/>kh\u00f4ng ph\u1ee5 thu\u1ed9c v\u00e0o gi\u00e1 tr\u1ecb bi\u1ebfn $x$. \u0110\u00fang hay sai?","select":["\u0110\u00fang","Sai"],"hint":"<br\/>Bi\u1ebfn \u0111\u1ed5i, r\u00fat g\u1ecdn bi\u1ec3u th\u1ee9c $P$. <br\/>\u00c1p d\u1ee5ng: Nh\u00e2n \u0111\u01a1n th\u1ee9c v\u1edbi t\u1eebng h\u1ea1ng t\u1eed c\u1ee7a \u0111a th\u1ee9c: $a(b+c) = a.b+a.c$<br\/>N\u1ebfu k\u1ebft qu\u1ea3 r\u00fat g\u1ecdn $P$ kh\u00f4ng ch\u1ee9a c\u00e1c bi\u1ebfn $x$ th\u00ec gi\u00e1 tr\u1ecb $P$ kh\u00f4ng ph\u1ee5 thu\u1ed9c v\u00e0o $x$ v\u00e0 ng\u01b0\u1ee3c l\u1ea1i.","explain":"<span class='basic_left'>Ta c\u00f3:<br\/>$ P=\\left( 5x-2 \\right)\\left( x+1 \\right)-\\left( x-3 \\right)\\left( 5x+1 \\right)-17\\left( x-2 \\right) $<br\/>$=5{{x}^{2}}+5x-2x-2-5{{x}^{2}}-x+15x+3-17x+34 $<br\/>$ =35 $<br\/>Gi\u00e1 tr\u1ecb c\u1ee7a $P$ kh\u00f4ng ph\u1ee5 thu\u1ed9c v\u00e0o c\u00e1c bi\u1ebfn $x$.<span><br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 \u0110\u00fang.<\/span>","column":2}]}],"id_ques":376},{"time":24,"part":[{"title":"\u0110i\u1ec1n v\u00e0o ch\u1ed7 tr\u1ed1ng ","title_trans":"","temp":"fill_the_blank","correct":[[["9"]]],"list":[{"point":10,"width":40,"type_input":"","ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai2/lv3/img\/1.png' \/><\/center>H\u1ec7 s\u1ed1 cao nh\u1ea5t c\u1ee7a \u0111a th\u1ee9c $C=\\left( 7x+3 \\right)\\left( 2x+1 \\right)$$-\\left( 5x-1 \\right)\\left( x+4 \\right)$ l\u00e0 _input_","hint":"Trong \u0111a th\u1ee9c m\u1ed9t bi\u1ebfn: H\u1ec7 s\u1ed1 cao nh\u1ea5t l\u00e0 h\u1ec7 s\u1ed1 \u0111i v\u1edbi bi\u1ebfn c\u00f3 l\u0169y th\u1eeba cao nh\u1ea5t.","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn<\/span><br\/> <b>B\u01b0\u1edbc 1:<\/b> Nh\u00e2n t\u1eebng h\u1ea1ng t\u1eed c\u1ee7a \u0111a th\u1ee9c n\u00e0y v\u1edbi t\u1eebng h\u1ea1ng t\u1eed c\u1ee7a \u0111a th\u1ee9c kia: $(a+b)(c+d) = ac+ad+bc+bd$<br\/> <b>B\u01b0\u1edbc 2:<\/b> S\u1eafp x\u1ebfp \u0111a th\u1ee9c theo l\u0169y th\u1eeba gi\u1ea3m d\u1ea7n v\u00e0 t\u00ecm b\u1eadc c\u1ee7a \u0111a th\u1ee9c \u0111\u00f3.<br\/><span class='basic_green'>Gi\u1ea3i<\/span><br\/>Ta c\u00f3:<br\/>$ C=\\left( 7x+3 \\right)\\left( 2x+1 \\right)$$-\\left( 5x-1 \\right)\\left( x+4 \\right) $<br\/>$ =14{{x}^{2}}+7x+6x+3-5{{x}^{2}}$$-20x+x+4 $<br\/>$ =9{{x}^{2}}-6x+7 $<br\/> \u0110a th\u1ee9c c\u00f3 l\u0169y th\u1eeba cao nh\u1ea5t c\u1ee7a bi\u1ebfn l\u00e0 $2$.<br\/> Do \u0111\u00f3 h\u1ec7 s\u1ed1 cao nh\u1ea5t l\u00e0 $9$.<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n c\u1ea7n \u0111i\u1ec1n l\u00e0 $9$.<\/span><\/span> "}]}],"id_ques":377},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 \u0111\u00fang nh\u1ea5t v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["17"],["7"]]],"list":[{"point":10,"width":40,"content":"","type_input":"","ques":"T\u00ecm $a$, bi\u1ebft: $\\left( a-5 \\right)\\left( -a+4 \\right)-\\left( a-1 \\right)\\left( a+3 \\right)$$=-2{{a}^{2}}$.<br\/>Gi\u00e1 tr\u1ecb c\u1ee7a $a$ c\u1ea7n t\u00ecm l\u00e0 $\\dfrac{\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}}{\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}} $","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn<\/span><br\/>Bi\u1ebfn \u0111\u1ed5i \u0111\u1eb3ng th\u1ee9c \u0111\u00e3 cho \u0111\u1ec3 t\u00ecm $a$. <br\/><span class='basic_green'>B\u00e0i gi\u1ea3i<\/span><br\/>Ta c\u00f3:<br\/>$\\left( a-5 \\right)\\left( -a+4 \\right)-\\left( a-1 \\right)\\left( a+3 \\right) $$=-2{{a}^{2}} $<br\/>$\\Leftrightarrow$ $ -{{a}^{2}}+4a+5a-20-{{a}^{2}}-3a+a+3$$=-2{{a}^{2}} $<br\/>$\\Leftrightarrow$ $ -2{{a}^{2}}+7a-17$$=-2{{a}^{2}} $<br\/>$\\Leftrightarrow$ $ 7a-17=0 $<br\/>$\\Leftrightarrow$ $ 7a=17 $<br\/>$\\Leftrightarrow$ $ a =\\dfrac{17}{7} $<br\/> <span class='basic_pink'> V\u1eady gi\u00e1 tr\u1ecb $a$ c\u1ea7n \u0111i\u1ec1n l\u00e0 $\\dfrac{17}{7}$.<\/span><\/span>"}]}],"id_ques":378},{"time":24,"part":[{"title":"\u0110i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng ","title_trans":"","temp":"fill_the_blank","correct":[[["5"]]],"list":[{"point":10,"width":40,"type_input":"","ques":"H\u1ec7 s\u1ed1 c\u1ee7a ${{x}^{4}}$ trong \u0111a th\u1ee9c $P=\\left( {{x}^{3}}-2{{x}^{2}}+x+1 \\right)\\left( 5x-1 \\right)$ l\u00e0 _input_","hint":"Ta \u0111i r\u00fat g\u1ecdn \u0111a th\u1ee9c \u0111\u00e3 cho, \u00e1p d\u1ee5ng: $(a+b)(c+d) = ac+ad+bc+bd$<br\/> T\u00ecm h\u1ec7 s\u1ed1 \u0111i v\u1edbi $x^4$","explain":"<span class='basic_left'>Ta \u0111i r\u00fat g\u1ecdn \u0111a th\u1ee9c:<br\/> $ P=\\left( {{x}^{3}}-2{{x}^{2}}+x+1 \\right)\\left( 5x-1 \\right) $<br\/>$ =5{{x}^{4}}-{{x}^{3}}-10{{x}^{3}}+2{{x}^{2}}$$+5{{x}^{2}}-x+5x-1 $<br\/>$ =5{{x}^{4}}-11{{x}^{3}}+7{{x}^{2}}+4x-1$<br\/> H\u1ec7 s\u1ed1 \u0111i v\u1edbi $x^4$ l\u00e0 $5$. <br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n c\u1ea7n \u0111i\u1ec1n l\u00e0 $5$.<\/span><\/span> "}]}],"id_ques":379},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":10,"ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai2/lv3/img\/1.png' \/><\/center>Khai tri\u1ec3n bi\u1ec3u th\u1ee9c $\\left( x+3 \\right)\\left( {{x}^{2}}-3x+9 \\right)$$-\\left( 54+{{x}^{3}} \\right)$ \u0111\u01b0\u1ee3c k\u1ebft qu\u1ea3 l\u00e0:","select":["A. $2x^3-27$ ","B. $-27$ ","C. $3{{x}^{2}}-27$","D. $2{{x}^{3}}-{{x}^{2}}+27$"],"hint":"Nh\u00e2n t\u1eebng h\u1ea1ng t\u1eed c\u1ee7a \u0111a th\u1ee9c n\u00e0y v\u1edbi t\u1eebng h\u1ea1ng t\u1eed c\u1ee7a \u0111a th\u1ee9c kia: $(a+b)(c+d) = ac+ad+bc+bd$","explain":"<span class='basic_left'>Ta th\u1ef1c hi\u1ec7n ph\u00e9p nh\u00e2n:<br\/> $ \\left( x+3 \\right)\\left( {{x}^{2}}-3x+9 \\right)-\\left( 54+{{x}^{3}} \\right) $<br\/>$ ={{x}^{3}}-3{{x}^{2}}+9x+3{{x}^{2}}-9x+27-54-{{x}^{3}} $<br\/>$ =-27 $<span><br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 B.<\/span>","column":2}]}],"id_ques":380}],"lesson":{"save":0,"level":3}}