For what value of x is the double product of the binomials x+2 and x-2 is 16 less than the sum of their squares?

(x + 2) (x - 2) = (x+2) ^2 + (x - 2) ^2 - 16

x^2 - 4 = 2x^2 + 4x - 4x + 8 - 16

x^2 - 4 = 2x^2 - 8

x^2 = 4

x = + / - 2

x = - 2 is the only value which fits the original equation so that's the answer.