Giúp mik bài 8 với các bạn
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\(8,\\ 1.A=2xy\left(x^2-y^2-2y-1\right)\\ 3.A=x^3\left(x^2-7\right)^2-36x=x\left[x^2\left(x^2-7\right)^2-36\right]\\ =x\left\{\left[x\left(x^2-7\right)-6\right]\left[x\left(x^2-7\right)+6\right]\right\}\\ =x\left(x^3-7x-6\right)\left(x^3-7x+6\right)\\ =x\left(x-3\right)\left(x+1\right)\left(x+2\right)\left(x+3\right)\left(x-2\right)\left(x-1\right)\\ 6.A=2x^4-32=2\left(x^4-16\right)\\ =2\left(x^2-4\right)\left(x^2+4\right)=2\left(x-2\right)\left(x+2\right)\left(x^2+4\right)\)
\(8.A=x^2\left(x^2-4x+4\right)=x^2\left(x-2\right)^2\\ 10.A=5\left(x^4-2x^2y^2+y^4\right)\\ =5\left(x^2-y^2\right)^2=5\left(x-y\right)^2\left(x+y\right)^2\\ 11.A=4\left(x-y\right)+\left(x-y\right)^2=\left(x-y\right)\left(4+x-y\right)\\ 12.A=x^4-\left(x^2-2x+1\right)=x^4-\left(x-1\right)^2=\left(x^2-x+1\right)\left(x^2+x-1\right)\\ 13.A=x^3-x^2-3x^2+3x+x-1=\left(x-1\right)\left(x^2-3x+1\right)\)
\(a,\frac{x+8}{3}+\frac{x+7}{2}=-\frac{x}{5}\)
\(\Leftrightarrow\frac{10\cdot\left(x+8\right)}{30}+\frac{15\left(x+7\right)}{30}=\frac{-6x}{30}\)
\(\rightarrow10x+80+15x+105=-6x\)
\(\Leftrightarrow31x+185=0\)
\(\Leftrightarrow x=-\frac{185}{31}\)
b,\(b,\frac{x-8}{3}+\frac{x-7}{4}=4+\frac{1-x}{5}\)
\(\Leftrightarrow\frac{20\left(x-8\right)}{60}+\frac{15\left(x-7\right)}{60}=\frac{240}{60}+\frac{12\left(1-x\right)}{60}\)
\(\rightarrow20x-160+15x-105=240+12-12x\)
\(\Leftrightarrow47x-517=0\)\(\Leftrightarrow x=11\)
a)67/81
b)140/96
HT
Nếu đúng k mình nha
Thanks mọi người nhìu