a) (x-2)(x+4)= x²+4x-2x-8=x²+2x-8
b) (y+2)(1-x)=y-yx+2-2x
c) (x-5)(2-x)=2x-x²-10+5x=-x²+7x-10
d) (m-3)(m-1)=m²-m-3m+3=m²-4m+3
e) (a-5)(6-a)=6a-a²-30+5a=-a²+11a-30
f) (2x-1)(x-3)=2x²-6x-1x+3=2x²-7x+3
g) (5-3x)(-2)=-10+6x
h) (3-2a)(2a-5)=6a-15-4a²+10a=-4a²+16a-15