(2x - y)3 - (2x - y)
= (2x - y)((2x - y)2 - 1)
= (2x - y)((2x - y)2 - (1)2)
Using the formula
[∵ (x2 - y2) = (x + y)(x - y)]
= (2x - y)((2x - y) - 1)((2x - y) + 1)
= (2x - y)(2x - y - 1)(2x - y + 1)
Hence, (2x - y)3 - (2x - y) = (2x - y)(2x - y - 1)(2x - y + 1)