Make first an equation out of it and try to understand how these numbers relate
In order to prove it by induction u have to prove that it is true for n=3
and then assume that it is true for some n and that it then follows for n+1
Is it true for 3?
Good not we assume that it is true for n and prove that it then follows for n+1.
and almost done now =).
n^2>2n by our first assumtion.
so we can subtract that from the inequality.
then we are left with 2n+1>1
and since n=positive number clearly this is true...
Hope I was clear enough can you take it from here