If you're considering real numbers only (and not complex/imaginary ones), then x^3 = 8 has only one solution and it is x = 2. We don't have the plus minus going on here. This is because (-2)^3 = -8 and not 8. We have three copies of -2 multiplied out to make a negative result.
If you consider complex/imaginary solutions, then x^3 = 8 has three solutions. The other two solutions are [tex]-1+i\sqrt{3}[/tex] and [tex]-1-i\sqrt{3}[/tex] where [tex]i = \sqrt{-1}[/tex]. If your teacher hasn't covered this chapter yet, then ignore this paragraph.
