Could someone please help me with these questions;I was having trouble with these four questions.

Question

Evaluate each limit, if it exists, using any appropriate technique.

1.) The limit as u approaches 4; u^2-16/u^3-64

2.) The limit as x approaches 1; x^3+ x^2-5x+3/ x^2-2x+1

3.) The limit as u approaches 1; square root(1+u) - square root(1+u^2)/ u-1

4.) The limit as x approaches 3 from the right; x square root(x-3)

Thank you.