(x+9)(x-9)=-21

Solution for (x+9)(x-9)=-21 equation:

Simplifying
(x + 9)(x + -9) = -21

Reorder the terms:
(9 + x)(x + -9) = -21

Reorder the terms:
(9 + x)(-9 + x) = -21

Multiply (9 + x) * (-9 + x)
(9(-9 + x) + x(-9 + x)) = -21
((-9 * 9 + x * 9) + x(-9 + x)) = -21
((-81 + 9x) + x(-9 + x)) = -21
(-81 + 9x + (-9 * x + x * x)) = -21
(-81 + 9x + (-9x + x2)) = -21

Combine like terms: 9x + -9x = 0
(-81 + 0 + x2) = -21
(-81 + x2) = -21

Solving
-81 + x2 = -21

Solving for variable 'x'.

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

Add '81' to each side of the equation.
-81 + 81 + x2 = -21 + 81

Combine like terms: -81 + 81 = 0
0 + x2 = -21 + 81
x2 = -21 + 81

Combine like terms: -21 + 81 = 60
x2 = 60

Simplifying
x2 = 60

Take the square root of each side:
x = {-7.745966692, 7.745966692}