Đáp án:
Giải thích các bước giải:
$2.$
$a,7x-35y=7(x-5y)$
$b,x^3-2x^2y+xy^2-9x=x(x^2-2xy+y^2-9)=x[(x-y)^2-9]=x(x-y-3)(x-y+3)$
$c,x^2-25=(x-5)(x+5)$
$d,x^2+2xy+y^2-36=(x+y)^2-36=(x+y-6)(x+y+6)$
$e,3(x-1)+y(1-x)$
$=3(x-1)-y(x-1)$
$=(3-y)(x-1)$
$3.$
$a,2x^2-7x=0$
$⇔x(2x-7)=0$
⇔\(\left[ \begin{array}{l}x=0\\x=\dfrac{7}{2}\end{array} \right.\)
$b,4x(x+2)-(x+1)(3x-5)=x(x-2)+8$
$⇔4x^2+8x-3x^2+5x-3x+5=x^2-2x+8$
$⇔x^2+10x-x^2+2x=8-5$
$⇔12x=3$
$⇔x=\dfrac{1}{4}$
$d,x^2-9=0$
$⇔(x-3)(x+3)=0$
⇔\(\left[ \begin{array}{l}x=3\\x=-3\end{array} \right.\)
