Test it for n=2 to show its positive.
Assume its >0 for n
Set n=n+1 and expand the equation but dont add the parts together. This should give .
Now do the same process on the part of this equation thats in brackets to prove its also positive, if it is, that means the entire equation above is positive. Hence positive for the inductive case n=2, n and n+1 hence +ve for all
It is for n=2;
Assume it is for n;
Let n=n+1 and expand the equation to give since we assumed and is clearly greater than 0.
So its positive for the base case n=2, n and n+1, hence +ve for all
Sorry i wrote this in a hurry if its unclear let me know.