-r^2-15r-36=0

Solution for -r^2-15r-36=0 equation:

Simplifying
-1r2 + -15r + -36 = 0

Reorder the terms:
-36 + -15r + -1r2 = 0

Solving
-36 + -15r + -1r2 = 0

Solving for variable 'r'.

Factor out the Greatest Common Factor (GCF), '-1'.
-1(36 + 15r + r2) = 0

Factor a trinomial.
-1((12 + r)(3 + r)) = 0

Ignore the factor -1.
Subproblem 1
Set the factor '(12 + r)' equal to zero and attempt to solve:

Simplifying
12 + r = 0

Solving
12 + r = 0

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

Add '-12' to each side of the equation.
12 + -12 + r = 0 + -12

Combine like terms: 12 + -12 = 0
0 + r = 0 + -12
r = 0 + -12

Combine like terms: 0 + -12 = -12
r = -12

Simplifying
r = -12
Subproblem 2
Set the factor '(3 + r)' equal to zero and attempt to solve:

Simplifying
3 + r = 0

Solving
3 + r = 0

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

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

Combine like terms: 3 + -3 = 0
0 + r = 0 + -3
r = 0 + -3

Combine like terms: 0 + -3 = -3
r = -3

Simplifying
r = -3
Solution
r = {-12, -3}