-0.0583 = x^-2
Solve for x.
What do you have to do to -0.0583 to find x?
Just remember that $\displaystyle x^{-a} = \frac {1}{x^a}$.
So you need to solve $\displaystyle -0.0583 = \frac {1}{x^2}$. Which should be pretty easy.
Hope that helps!
EDIT: Just noticed there's a wrinkle here, since the answer involves the square root of a negative number. So the actual answer is imaginary (i.e. a complex number). Still, that aside, that's how negative exponents basically work.