The solutions to the equation are +3 and -3.
This equation is called a perfect square binomial because it can be factored as a difference of two squares. To solve, first, you have to factor out like terms. In this case, you would factor out a 9 from the equation. Then, solve for X.
9x² - 81 = 0
9(x² - 9) = 0
x² - 9 + 9 = 0 + 9
√x² = √9
x = +3, -3
