d) (a + b + c)^2 = a^2 + b^2 + c^2 + 2ab + 2ac + 2bc.
d) (a + b + c)2 = a2 + b2 + c2 + 2ab + 2ac + 2bc.
d) (a + b + c)2 = [(a + b) + c]2
= (a + b)2 + 2(a + b)c + c2
= a2 + 2ab + b2 + 2ac + 2bc + c2
= a2 + b2 + c2 + 2ab + 2ac + 2bc.