PLEASE HELP!!!

Simplify:
1) -sqrt(-9y^2) if y < 0
2) 3sqrt(c^2) if c is greater then or equal to 0
3) -5sqrt(4x^2) if x is greater than or equal to 0
4) -5sqrt(y^2) if y > 0
5) 0.5sqrt(16a^2) if a < 0