Please help me to prove that f(n)=(n^m) and f(n)=(n^m)

Prove that if f(n)=amn^m++a1n+a0 and am>0, then f(n)=(n^m)

Prove that ifMm)-@mn"+ tain+ao and @m>0, thenfo)=(n") Prove that iffn)-ann+tantao and a 0, then An)-O(n")