Question

what is the soulution of x^2 + 64 = 0

Answer 1

Solve out
x^2 + 64 = 0
x^2 = -64 ( we are going to use imaginary numbers to solve)
x = $i \sqrt{64}$
x = 8i, -8i final answers

Answer 2

8i.

This boils down to what is the square root of -64. Negative numbers can't be squares so an imaginary number is part of your answer.