5) (2х-1)×(2x+y);
6) (m-n)×(x+y);
7) (5-a)×(4-a);
8) (6m-3)×(2-5m).​

1) (x+m)(y+m)=xy+xm+my+m²

2) (x+8)(x-1)=x²-x+8x-8=x²+7x-8

3) (-a+y)(-y-2)=ay+2a-y²-2y

4) (a-4)(2a+1)=2a²+a-8a-4=2a²-7a-4

5) (2x-1)(2x+y)=4x²+2xy-2x-y

6) (m-n)(x+y)=mx+my-nx-ny

7) (5-a)(4-a)=20-5a-4a+a²=a²-9a+20

8) (6m-3)(2-5m)=12m-30m²-6+15m=-30m²+27m-6