title: Big O Notation of an expression
body: <p>If I have an algorithm that takes 4n^2 + 7n moves to accomplish, what is its O? 
  O(4n^2)?
  O(n^2)?</p>
  
  <p>I know that 7n is cut off, but I don't know if I should keep the n^2 coefficient or not.</p>
  
  <p>Thanks</p>