(x-1)(x+4)-(x-1)² -3(x-1)=(x-1)(x+4-x+1-3)=2(x-1)
(a-b)(x+3)+(b-a)(2x-1)-(a-b)(x+7)=(a-b)(x+3)-(a-b)(2x-1)-(a-b)(x+7)=
=(a-b)(x+3-2x+1-x-7)=(a-b)(-2x-3)=
(x+1)(x-4)+(4-x)(x+2)-x(x-4) =(x+1)(x-4)-(x-4)(x+2)-x(x-4) =
=(x-4)(x+1-x-2-x) =(x-4)(-1-x) =(4-x)(1+x)
(2x-1)(x+5)+(2x-1)² -2x²+x
=
=(2x-1)(x+5)+(2x-1)² -x(2x-1)
=
=(2x-1)(x+5+2x-1 -x)
=
=(2x-1)(2x+4)
=2(2x-1)(x+2)