-m^2-9m-20=0

Solution for -m^2-9m-20=0 equation:

Simplifying
-1m2 + -9m + -20 = 0

Reorder the terms:
-20 + -9m + -1m2 = 0

Solving
-20 + -9m + -1m2 = 0

Solving for variable 'm'.

Factor out the Greatest Common Factor (GCF), '-1'.
-1(20 + 9m + m2) = 0

Factor a trinomial.
-1((5 + m)(4 + m)) = 0

Ignore the factor -1.
Subproblem 1
Set the factor '(5 + m)' equal to zero and attempt to solve:

Simplifying
5 + m = 0

Solving
5 + m = 0

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

Add '-5' to each side of the equation.
5 + -5 + m = 0 + -5

Combine like terms: 5 + -5 = 0
0 + m = 0 + -5
m = 0 + -5

Combine like terms: 0 + -5 = -5
m = -5

Simplifying
m = -5
Subproblem 2
Set the factor '(4 + m)' equal to zero and attempt to solve:

Simplifying
4 + m = 0

Solving
4 + m = 0

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

Add '-4' to each side of the equation.
4 + -4 + m = 0 + -4

Combine like terms: 4 + -4 = 0
0 + m = 0 + -4
m = 0 + -4

Combine like terms: 0 + -4 = -4
m = -4

Simplifying
m = -4
Solution
m = {-5, -4}