Concept: 1 Mark
Application: 3 Marks
2x3a−6x2aya+6xay2a−2y3a
=2(x3a−3x2aya+3xay2a−y3a)
=2{(xa)3−(ya)3−3xaya(xa−ya)} [∵x3a=(xa)3 and y3a=(ya)3]
Using the identity a3−b3−3ab(a−b)=(a−b)3
=2(xa−ya)3
2xa−2ya=2(xa−ya)
∴ 2x3a−6x2aya+6xay2a−2y3a2xa−2ya=2(xa−ya)32(xa−ya)
=(xa−ya)2