d) (1 + x + x^2)(1 + x – x^2).
d) (1 + x + x2)(1 + x – x2).
d) (1 + x + x2)(1 + x – x2) = (1 + x)2 ‒ (x2)2
= 1 + 2.1.x + x2 ‒ x4 = 1 + 2x + x2 ‒ x4.