(a+3)(b-7)=ab-7b+3b-21
(a-5)(11-b)= 11a-ab- 55+5b
(x-4)(x+8)= x²+8x -4x-24
(x-5)(9-x) =9x-x²-45+5x
(3a+5)(3a-6)+30= 9a²+18a+15a+30+30= 9a²+33a+60
8x-(3x+1)(5x+1)= 8x-( 15x²+3x+5x+1)= 8x-15x²-3x-5x-1= -15x²-1
(y+2)(y+3)-y(y-1)= y²+3y+2y+6-y²+y=6y+6=6(y+1)