Đáp án:
$1 ,A =5x(x-1)-15x .(1-x)$
$ = 5x(x-1) +15x.(x-1)$
$ =(x-1)(5x+15x)$
$ = 20x(x-1)$
$2, A = 2x^2 .(x-1) -15x.(1-x)$
$ =2x^2.(x-1) +15x(x-1)$
$ = (x-1)(2x^2+15x)$
$=x(2x+15)(x-1)$
$3,A = 9x^2 .(y+z) +3x(y+z)$
$ = (y+z)(9x^2+3x)$
$=3x(3x+1)(y+z)$
$4,A = 10x(x-y) -8y.(y-x)$
$ = 10x(x-y) +8y(x-y)$
$=(x-y)(10x+8y)$
$= 2(5x+4y)(x-y)$
$ 5,A = 2x.(x+y) -6x^2 .(x+y)$
$ = (x+y)(2x-6x^2)$
$=2x(1-3x)(x+y)$
$ 6,A = 10xy .(x-y)-6y.(y-x)$
$ = 10xy .(x-y) +6y(x-y)$
$ =(x-y)(10xy-6y)$
$=2y(5x-3)(x-y)$