1) (a-b)(2a-3b)-(3a-b)(2a+b)=2a^2-3ab-2ab+3b^2-6a^2-3ab+2ab+b^2=-4a^2-6ab+4b^2=-2(2a^2+3ab-2b^2)

2) 2x(x-4)+(x+5)(x+3)=2x^2-8x+x^2+8x+15=3x^2+15=3(x^2+5)

3) x(x+y)-(y-1)(x-1)=x^2+xy-xy+y+x-1=x^2+x+y-1

4) (3a-b)(b+3a)+(4a-b)(a-4b)=3ab+9a^2-b^2-3ab+4a^2-16ab-ab+4b^2=13a^2+3b^2-17ab

1) (a-b)(2a-3b)-(3a-b)(2a+b) = 2a2-3ab-2ab+3b2 -6a2-3ab+2ab+b2 = -4a2-6ab+4b2

2) 2x(x-4)+(x+5)(x+3) = 2x2-8x+x2+3x+5x+15 = 3x2+15

3) x(x+y)-(y-1)(x-1) = x2+xy-xy+y+x-1 = x2+y-1

4) (3a-b)(b+3a)+(4a-b)(a-4b) = 3ab+9a2-b2-3ab+4a2-16ab-ab+4b2 =13a2-17ab+3b2