1) (a-b)(2a-3b)-(3a-b)(2a+b)
2a²-3ab-2ab+3b²-(6a²+3ab-2ab-b²)
2a²-5ab+3b²-6a²-ab+b²
-4a²-6ab+4b²
2) 2x(x-4)+(x+5)(x+3)
2x²-8+x²+3x+5x+15
3x²+8x+7
3) x(x+y)-(y-1)(x-1)
x²+xy-(xy-y-x+1)
x²+xy-xy+y+x-1
x²+y+x-1
4) (3a-b)(b+3a)+(4a-b)(a-4b)
3ab+9a²-b²-3ab+(4a²-16ab-ab+4b²)
9a²-b²+4a²-17ab+4b²
13a²+3b²-17ab