Posted by Anonymous on Saturday, October 29, 2011 at 11:10pm.
I think it should help to notice that 5n^2 + 6n + 3 = 3n^2 + 6n + 3 + 2n^2 = 3(n+1)^2 + 2n^2 So, what you have is just 3/n^2 + 2/(n+1)^2