=(3x+9)(3x-9)

Solution for =(3x+9)(3x-9) equation:

Simplifying
0 = (3x + 9)(3x + -9)

Reorder the terms:
0 = (9 + 3x)(3x + -9)

Reorder the terms:
0 = (9 + 3x)(-9 + 3x)

Multiply (9 + 3x) * (-9 + 3x)
0 = (9(-9 + 3x) + 3x * (-9 + 3x))
0 = ((-9 * 9 + 3x * 9) + 3x * (-9 + 3x))
0 = ((-81 + 27x) + 3x * (-9 + 3x))
0 = (-81 + 27x + (-9 * 3x + 3x * 3x))
0 = (-81 + 27x + (-27x + 9x2))

Combine like terms: 27x + -27x = 0
0 = (-81 + 0 + 9x2)
0 = (-81 + 9x2)

Solving
0 = -81 + 9x2

Solving for variable 'x'.

Move all terms containing x to the left, all other terms to the right.

Add '-9x2' to each side of the equation.
0 + -9x2 = -81 + 9x2 + -9x2
Remove the zero:
-9x2 = -81 + 9x2 + -9x2

Combine like terms: 9x2 + -9x2 = 0
-9x2 = -81 + 0
-9x2 = -81

Divide each side by '-9'.
x2 = 9

Simplifying
x2 = 9

Take the square root of each side:
x = {-3, 3}