a) 27x5 - x2
= x2.(27x3 - 1)
= x2 . [ (3x)3 - 13 ]
= x2.(3x - 1)(9x2 + 3x + 1)
b) x5 + 8x2
= x2 .(x3 + 8)
= x2 . (x3 + 23)
= x2 .(x + 2)(x2 - 2x + 4)
c) 2x - 2y - x2 + 2xy - y2
= (2x - 2y) - (x2 - 2xy + y2)
= 2.(x - y) - (x - y)2
= (x - y)(2 - x + y)