-z^2-8z-15=0

Solution for -z^2-8z-15=0 equation:

Simplifying
-1z2 + -8z + -15 = 0

Reorder the terms:
-15 + -8z + -1z2 = 0

Solving
-15 + -8z + -1z2 = 0

Solving for variable 'z'.

Factor out the Greatest Common Factor (GCF), '-1'.
-1(15 + 8z + z2) = 0

Factor a trinomial.
-1((5 + z)(3 + z)) = 0

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

Simplifying
5 + z = 0

Solving
5 + z = 0

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

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

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

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

Simplifying
z = -5
Subproblem 2
Set the factor '(3 + z)' equal to zero and attempt to solve:

Simplifying
3 + z = 0

Solving
3 + z = 0

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

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

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

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

Simplifying
z = -3
Solution
z = {-5, -3}