a) (x+1)(x+3)²-4(x+1) = (x+1)((x+3)²-4) = (x+1)(x+3-2)(x+3+2) = (x+1)(x+1)(x+5) = (x+1)²(x+5)
b) (x+3)(2x+1)²-16(x+3) = (x+3)((2x+1)²-16) = (x+3)(2x+1-4)(2x+1+4) = (x+3)(2x-3)(2x+5)
c) = (x-3)(x+2)²-(x-3) = (x-3)((x+2)²-1) = (x-3)(x+2-1)(x+2+1) = (x-3)(x+1)(x+3)
d) = (x-4)(2x+1)²-(x-4) = (x-4)((2x+1)²-1) = (x-4)(2x+1-1)(2x+1+1) = 2x(x-4)(2x+2) = 4x(x-4)(x+1)
