I only need the answer to number 1

Prove that if f (n) = 13n^2 + 1234n + 91.2n square root n and g (n) = Theta (f (n)), then (f (n) + g (n))^2 = Theta (n^4). You may assume that n = O (n^2) and square root n = O (n). Prove the following exponentiation property of Big - Theta: if f (x) = Theta (g(x)), f (x)^n = Theta (g(x)^n) for any n > 1