$\text{a) x²-2x}$
$\text{= x(x-2)}$
$\text{b) 3x-6y}$
$\text{= 3(x-2y)}$
$\text{c) 5(x+3y)-15x(x+3y)}$
$\text{= (x+3y).(5-15x)}$
$\text{d) 3(x-y)-7x(y-x)}$
$\text{= 3(x-y)-7x[-(x+y)] }$
$\text{= 3(x-y)+7x(x-y)}$
$\text{=(3+7x)(x-y)}$
$\text{e) x²+6x}$
$\text{= x(x+6)}$
$\text{f) 2(x-y)+y(y-x)}$
$\text{= 2(x-y)+y[-(x+y)] }$
$\text{= 2(x-y)-y(x-y)}$
$\text{= (x-y)(2-y)}$
$\text{Học tốt!!!}$
