# Homework Help: Complex numbers root problems

1. Sep 4, 2011

### alwaysconfuse

1. The problem statement, all variables and given/known data
What is the square root of z=-9

2. Relevant equations

3. The attempt at a solution
Is it possible of me to not use De'Moivre's theorem to solve this question??
Solution :
z= $\sqrt{-9}$
z=$\sqrt{9}$ x $\sqrt{}-1$
z=$\pm3$ i

Will this method be acceptable?? Is this still under the topic complex roots?

2. Sep 5, 2011