Hello! I'm having a bit of trouble working out how the following expression is factorised.

1/4nˆ2 (n+1)ˆ2 – 1/2n(n+1)

Here is the answer

= 1/4n(n+1)(nˆ2+n-2)

If anybody could show a working of how that answer is acheived it would be much appreciated.

Thanks!