15d^2-40d-15=0

Solution for 15d^2-40d-15=0 equation:

Simplifying
15d2 + -40d + -15 = 0

Reorder the terms:
-15 + -40d + 15d2 = 0

Solving
-15 + -40d + 15d2 = 0

Solving for variable 'd'.

Factor out the Greatest Common Factor (GCF), '5'.
5(-3 + -8d + 3d2) = 0

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

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

Simplifying
-1 + -3d = 0

Solving
-1 + -3d = 0

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

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

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

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

Divide each side by '-3'.
d = -0.3333333333

Simplifying
d = -0.3333333333
Subproblem 2
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
Solution
d = {-0.3333333333, 3}