а) (2+b) (3b+2)

б) (5b-b^2) (2+3b)

в) (2-b) (3-5b)

г) (-3b-4) (2b-5)

a) (2+b) (3b+2) = 6b+4+3b^2+2b=8b+3b^2+4

b) (5b-b^2) (2+3b) = 10b+15b^2-2b^2-3b^3=-3b^3+10b+13b^2

в) (2-b) (3-5b) = 6-10b-3b+5b^2=5b^2-13b+6

г) (-3b-4) (2b-5) = - 6b^2+15b-8b+20=-6b^2+7b+20