(x-9)(x+1)+8x=0

Solution for (x-9)(x+1)+8x=0 equation:

Simplifying
(x + -9)(x + 1) + 8x = 0

Reorder the terms:
(-9 + x)(x + 1) + 8x = 0

Reorder the terms:
(-9 + x)(1 + x) + 8x = 0

Multiply (-9 + x) * (1 + x)
(-9(1 + x) + x(1 + x)) + 8x = 0
((1 * -9 + x * -9) + x(1 + x)) + 8x = 0
((-9 + -9x) + x(1 + x)) + 8x = 0
(-9 + -9x + (1 * x + x * x)) + 8x = 0
(-9 + -9x + (1x + x2)) + 8x = 0

Combine like terms: -9x + 1x = -8x
(-9 + -8x + x2) + 8x = 0

Reorder the terms:
-9 + -8x + 8x + x2 = 0

Combine like terms: -8x + 8x = 0
-9 + 0 + x2 = 0
-9 + x2 = 0

Solving
-9 + x2 = 0

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 = 0 + 9

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

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

Simplifying
x2 = 9

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