d) a^3 – b^3 + 4ab + 4a^2 + 4b^2
d) a3 – b3 + 4ab + 4a2 + 4b2
d) a3 – b3 + 4ab + 4a2 + 4b2
= (a3 – b3) + (4a2 + 4ab + 4b2)
= (a ‒ b)(a2 + ab + b2) + 4.(a2 + ab + b2)
= (a2 + ab + b2)(a – b + 4).