3х²-12х = 3х(х-4)
ab-2a+b²-2b = (ab-2a)+(b²-2b) = a(b-2)+b(b-2) = (a+b)(b-2)
4x²-9 = (2x-3)(2x+3)
x³-8x²+16x = x(x²-8x+16) = x(x-4)² = x(x-4)(x-4)
