First, we need to get the X variable by itself. To do this, we need to add 9 to both sides.
X^2 - 9 = 0
X^2 - 9 + 9 = 0 + 9
X^2 = 9
Now, we need to take the square root of both sides.
√(X^2) = √9
The square root of any squared number is the number itself. Thus:
√(X^2) = +/-√9
X = +/-√9
X = +/-3
Thus:
X = 3 and X = -3