You have the following equation:
x² = -64
In order to solve the previoues equation you proceed as follow:
x² = -64 apply square root both sides
√x² = ± √(-64)
x = ± √(-64) replace 64 by 8²
x = ± √(-8²) rewrite -8² as (-1)(8²)
x = ± √((-1)(8²)) calculate square root of 8²
x = ± 8√(-1) use the fact that by definition √(-1) = i
x = ± 8i
Hence, the previous equation has two complex solutions:
x = 8i
x = -8i
