Rewrite as .

Since both terms are perfect squares, factor using the difference of squares formula, where and .

If any individual factor on the left side of the equation is equal to , the entire expression will be equal to .

Set the first factor equal to .

Subtract from both sides of the equation.

Set the next factor equal to .

Add to both sides of the equation.

The final solution is all the values that make true.

Solve by Factoring x^2-81=0