Mathematically proof for Big-O related topic

Job ID: 34117790

Budget: $10 – $11 CAD

I need a clear proof for below equation:
O(n^k)+O(n^m)=O(N^m) m>k>0

Using Big-O formal definition.

FIXED PRICE=10CAD
I have to pay the site charge like you. OK?
Related categories: Mathematics Computer Science