(n+1)(n-9)=0

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

Simplifying
(n + 1)(n + -9) = 0

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

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

Multiply (1 + n) * (-9 + n)
(1(-9 + n) + n(-9 + n)) = 0
((-9 * 1 + n * 1) + n(-9 + n)) = 0
((-9 + 1n) + n(-9 + n)) = 0
(-9 + 1n + (-9 * n + n * n)) = 0
(-9 + 1n + (-9n + n2)) = 0

Combine like terms: 1n + -9n = -8n
(-9 + -8n + n2) = 0

Solving
-9 + -8n + n2 = 0

Solving for variable 'n'.

Factor a trinomial.
(-1 + -1n)(9 + -1n) = 0

Subproblem 1
Set the factor '(-1 + -1n)' equal to zero and attempt to solve:

Simplifying
-1 + -1n = 0

Solving
-1 + -1n = 0

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

Add '1' to each side of the equation.
-1 + 1 + -1n = 0 + 1

Combine like terms: -1 + 1 = 0
0 + -1n = 0 + 1
-1n = 0 + 1

Combine like terms: 0 + 1 = 1
-1n = 1

Divide each side by '-1'.
n = -1

Simplifying
n = -1
Subproblem 2
Set the factor '(9 + -1n)' equal to zero and attempt to solve:

Simplifying
9 + -1n = 0

Solving
9 + -1n = 0

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

Add '-9' to each side of the equation.
9 + -9 + -1n = 0 + -9

Combine like terms: 9 + -9 = 0
0 + -1n = 0 + -9
-1n = 0 + -9

Combine like terms: 0 + -9 = -9
-1n = -9

Divide each side by '-1'.
n = 9

Simplifying
n = 9
Solution
n = {-1, 9}