I need help with this question. If you could explain and give the anwser it would help so much! :)

I need help with this question. If you could explain and give the anwser it would help so much! :)

 

Find all complex numbers z such that z^4 = -4

 

Note: All solutions should be expressed in the form a + bi, where a and b are real numbers.

 

Thanks again! :)