1. Find a formula for the sum http://alt2.artofproblemsolving.com/...894c1b290f.gif

2. Find the sum of http://alt2.artofproblemsolving.com/...5c62244619.gif

3. Find a formula for http://alt2.artofproblemsolving.com/...8126ed417e.gif

Can anyone please solve step by step, I just started summations and need to see the procedure of doing these questions

Thanks!