Question

Find the value of (x + y)2 + (x - y)2.​

Answer 1

This is in the form of a^2 - b^2 = (a + b) * (a - b)

Thus, (x + y)^2 - (x - y)^2 = (x + y + x - y) * (x + y - x + y)

                                                   = 2x * 2y

                                                   = 4xy

Thus, (x + y)^2 - (x - y)^2 = 4xy.