(4a-b)(a-6b)+a(25b-3a)= 4a²-24ab-ab+6b²+25ab-3a²=a²+b²
(2x+3y)(x-y)-x(x+y)=2x²-2xy+3xy-3y²-x²-xy=x²-3y²
3a(a+1)+(a+2)(a-3)=3a²+3a+a²-3a+2a-6=4a²+2a-6
2c(5c-3)+(c-2)(c-4)=10c²-6c+c²-4c+8-2c=11c²-12c+8
(3a+b)(a-2b)+(2a+b(a-5b)=3a²-6ab+ab-2b²+2a²-10ab+ab-5b²=5a²-14ab-7b²
(x+1)(x+7)-(x+2)(x+3)=x²+7x+x+7-x²-3x-2x-6=3x+1
(a-4)(a+6)+(a-10)(a-2)=a²+6a-4a-24+a²-2a+10a-20=2a²+10a-44
(y-3)(5-y)-(4-y)(y+6)=5y-y²-15+3y-4y-24+y²-6y=-2y-39