solve for x. express your answer in simplest radical form if necessary
x^2 - 81
To solve for x, we need to set the equation equal to zero and use the difference of squares formula to factor it.
x^2 - 81 = 0
(x - 9)(x + 9) = 0
Now, set each factor equal to zero and solve for x:
x - 9 = 0 or x + 9 = 0
x = 9 or x = -9
Therefore, the solutions for x are x = 9 and x = -9.