Question 91370
Show by counterexample that (x+y)^-2 and x^-2 + y^-2 are not equivalent.

let x=1, y=1

{{{(x+y)^(-2)}}} = {{{2^(-2)}}} = {{{1/4}}}

{{{x^(-2) + y^(-2)}}} = {{{1^(-2) + 1^(-2)}}} = 1+1 = 2

apparently they are not equal.