(x+4)(x-4)-9=0

Solution for (x+4)(x-4)-9=0 equation:

Simplifying
(x + 4)(x + -4) + -9 = 0

Reorder the terms:
(4 + x)(x + -4) + -9 = 0

Reorder the terms:
(4 + x)(-4 + x) + -9 = 0

Multiply (4 + x) * (-4 + x)
(4(-4 + x) + x(-4 + x)) + -9 = 0
((-4 * 4 + x * 4) + x(-4 + x)) + -9 = 0
((-16 + 4x) + x(-4 + x)) + -9 = 0
(-16 + 4x + (-4 * x + x * x)) + -9 = 0
(-16 + 4x + (-4x + x2)) + -9 = 0

Combine like terms: 4x + -4x = 0
(-16 + 0 + x2) + -9 = 0
(-16 + x2) + -9 = 0

Reorder the terms:
-16 + -9 + x2 = 0

Combine like terms: -16 + -9 = -25
-25 + x2 = 0

Solving
-25 + x2 = 0

Solving for variable 'x'.

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

Add '25' to each side of the equation.
-25 + 25 + x2 = 0 + 25

Combine like terms: -25 + 25 = 0
0 + x2 = 0 + 25
x2 = 0 + 25

Combine like terms: 0 + 25 = 25
x2 = 25

Simplifying
x2 = 25

Take the square root of each side:
x = {-5, 5}