d) x^6 + y^9
d) x6 + y9
d) x6 + y9
= (x2)3 + (y3)3
= (x2 + y3)[(x2)2 ‒ x2.y3 + (y3)2]
= (x2 + y3)(x4 ‒ x2y3 + y6).