If (a+b)^2=100 and (a−b)^2=64 What is the value of a^2+b^2?
(A) 66 (B) 18 (C) 82 (D) 164 (E) 36
i got c
your copy/paste mangled the 2nd expression, but if it is (a-b)^2 = 64, then
(a+b)^2 + (a-b)^2
= a^2+2ab+b^2 + a^2-2ab+b^2
= 2(a^2+b^2)
so,
2(a^2+b^2) = 100+64
a^2+b^2 = 82