d^2-2d-15=0

Solution for d^2-2d-15=0 equation:

Simplifying
d2 + -2d + -15 = 0

Reorder the terms:
-15 + -2d + d2 = 0

Solving
-15 + -2d + d2 = 0

Solving for variable 'd'.

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

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

Simplifying
-3 + -1d = 0

Solving
-3 + -1d = 0

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

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

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

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

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

Simplifying
d = -3
Subproblem 2
Set the factor '(5 + -1d)' equal to zero and attempt to solve:

Simplifying
5 + -1d = 0

Solving
5 + -1d = 0

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

Add '-5' to each side of the equation.
5 + -5 + -1d = 0 + -5

Combine like terms: 5 + -5 = 0
0 + -1d = 0 + -5
-1d = 0 + -5

Combine like terms: 0 + -5 = -5
-1d = -5

Divide each side by '-1'.
d = 5

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