Let n be a natural number. Using modular arithmetic (do not use mathematical induction), prove that… Show more Let n be a natural number. Using modular arithmetic (do not use mathematical induction), prove that 7 divides 3^n+1 − 2^2n + 5^2n+1 if and only if n is even. (Hint: One approach is to consider the cases n even and n odd separately.) • Show less