a) (x+1) •(x+2)= x²+2x+x+2 = x²+3x+2
b) (x-3)•(x+7)= x²+7x-3x-21 = x²+4x-21
c) (2x+5)•(x-3)= 2x²-6x+5x-15 = 2x²-x-15
d) ( 1-2x)•(3x+4)= 3x+4-6x²-8x = -5x+4-6x² = -6x²-5x+4
e) (a+3)•(5a-2)= 5a²-2a+15a-6 = 5a²+13a-6
f) (x+y)•(2x-y)= 2x²-xy+2xy-y² = 2x² +xy - y²