(x+3)(x-3)=81

Solution for (x+3)(x-3)=81 equation:

Simplifying
(x + 3)(x + -3) = 81

Reorder the terms:
(3 + x)(x + -3) = 81

Reorder the terms:
(3 + x)(-3 + x) = 81

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

Combine like terms: 3x + -3x = 0
(-9 + 0 + x2) = 81
(-9 + x2) = 81

Solving
-9 + x2 = 81

Solving for variable 'x'.

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

Add '9' to each side of the equation.
-9 + 9 + x2 = 81 + 9

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

Combine like terms: 81 + 9 = 90
x2 = 90

Simplifying
x2 = 90

Take the square root of each side:
x = {-9.486832981, 9.486832981}