hello, I need help with this question

(a) Using the definition of O, prove that 7n4 n 15 E O(n) (b) Using the definition of S2, prove that n4 - 16n2 +n E (n4). (c) Compare the order of growth of f(n) logn and g(n) Vlog(n2). Justify your answer. (d) Compare the order of growth of f(n) -11" and g(n) - 12". Justify your answer. log Vn and g(n) log(n2). Justily y