r^2+8r=-15

Solution for r^2+8r=-15 equation:

Simplifying
r2 + 8r = -15

Reorder the terms:
8r + r2 = -15

Solving
8r + r2 = -15

Solving for variable 'r'.

Reorder the terms:
15 + 8r + r2 = -15 + 15

Combine like terms: -15 + 15 = 0
15 + 8r + r2 = 0

Factor a trinomial.
(5 + r)(3 + r) = 0

Subproblem 1
Set the factor '(5 + r)' equal to zero and attempt to solve:

Simplifying
5 + r = 0

Solving
5 + r = 0

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

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

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

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

Simplifying
r = -5
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 = {-5, -3}