solve each equation.

Question

x^4-81=0

Answer 1

factor it, you are looking at the difference of squares

x^4 - 81 = 0
(x^2 + 9)(x^ - 9) = 0 , and again
(x^2 + 9)(x+3)(x-3)= 0
x= -3 or x = +3 or x^2 = -9 ---> x = ± 3i

If you have not studied complex numbers, then just go with the
x = ± 3