Prove this restriction?

Question

prove that
a^(n)+b^(n) can never be expressed as difference of two coprime squares when "a" & "b" both r odd natural numbers & n>1.

Answer 1

Let a = 3, b - 5, and n = 3. Then a^n + b^n = 3^3 + 5^3 = 27 + 125 = 152 = 441 - 289 = 21^2 - 17^2, which are coprime squares. So maybe you left out something? Check your question.