18-3X-X^2=0

Solution for 18-3X-X^2=0 equation:

Simplifying
18 + -3X + -1X2 = 0

Solving
18 + -3X + -1X2 = 0

Solving for variable 'X'.

Factor a trinomial.
(3 + -1X)(6 + X) = 0

Subproblem 1
Set the factor '(3 + -1X)' equal to zero and attempt to solve:

Simplifying
3 + -1X = 0

Solving
3 + -1X = 0

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

Add '-3' to each side of the equation.
3 + -3 + -1X = 0 + -3

Combine like terms: 3 + -3 = 0
0 + -1X = 0 + -3
-1X = 0 + -3

Combine like terms: 0 + -3 = -3
-1X = -3

Divide each side by '-1'.
X = 3

Simplifying
X = 3
Subproblem 2
Set the factor '(6 + X)' equal to zero and attempt to solve:

Simplifying
6 + X = 0

Solving
6 + X = 0

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

Add '-6' to each side of the equation.
6 + -6 + X = 0 + -6

Combine like terms: 6 + -6 = 0
0 + X = 0 + -6
X = 0 + -6

Combine like terms: 0 + -6 = -6
X = -6

Simplifying
X = -6
Solution
X = {3, -6}