Đáp án + Giải thích các bước giải:
$a)7x+7y=7(x+y)$
$c)3x(x-1)+7x^2(x-1)=(x-1)(3x+7x^2)=x(x-1)(3+7x)$
$e)5y^{10}+15y^6=5y^6(y^4+3)$
$g)x^2y^2z+xy^2z^2+x^2yz^2= xyz(xy+yz+xz)$
$i)x^3+6x^2y+12xy^2+8y^3=(x+2y)^3$
$l)125x^3+y^6=(5x+y)(25x^2+5xy^2+y^4)$
$n)y^2(x^2+y)-zx^2-zy=y^2(x^2+y)-z(x^2+y)$
$=(x^2+y)(y^2-z)$
$p)3x(x+1)^2-5x^2(x+1)+7(x+1)$
$= (x+1)[3x(x+1)-5x^2+7]=(x+1)(3x^2+3x-5x^2+7)$
$=(x+1)(-2x^2+3x+7)$
$r)9(x+5)^2-(x-y)^2=[3(x+5)-x+y][3(x+5)+x-y]$
$=(3x+15-x+y)(3x+15+x-y)=(2x+y+15)(4x-y+15)$
$t)x^4-x^3-x^2+1= (x^4-x^3)-(x^2-1)$
$= x^3(x-1)-(x-1)(x+1)=(x-1)(x^3-x-1)$
