1. The problem statement, all variables and given/known data "This is an example from my textbook: Solve the equation z4 - 4z2 + 4 - 2i = 0 Solution: Rearranging, we get z4 - 4z2 + 4 = 2i or (z2 - 2)2 = 2i = (1+i)2 This has solutions z2 - 2 = 1+i or -1-i. Equivalently z2=3+i or z2=1-i These may be solved to give the 4 solutions of the original equation. " ========================== I don't understand the following step: (z2 - 2)2 = (1+i)2 => z2 - 2 = 1+i or -1-i Why is this true? I remember for real numbers we have √(x2) = |x| (note that it is |x|, not x). Is this true for complex numbers? If so, then (z2 - 2)2 = (1+i)2 => z2 - 2 = +/- √[(1+i)2] = +/- |1+i| ??? 2. Relevant equations N/A 3. The attempt at a solution Shown above. I hope someone can explain this. Any help is appreciated!