15c^2-13c-20=0

Solution for 15c^2-13c-20=0 equation:

Simplifying
15c2 + -13c + -20 = 0

Reorder the terms:
-20 + -13c + 15c2 = 0

Solving
-20 + -13c + 15c2 = 0

Solving for variable 'c'.

Factor a trinomial.
(-4 + -5c)(5 + -3c) = 0

Subproblem 1
Set the factor '(-4 + -5c)' equal to zero and attempt to solve:

Simplifying
-4 + -5c = 0

Solving
-4 + -5c = 0

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

Add '4' to each side of the equation.
-4 + 4 + -5c = 0 + 4

Combine like terms: -4 + 4 = 0
0 + -5c = 0 + 4
-5c = 0 + 4

Combine like terms: 0 + 4 = 4
-5c = 4

Divide each side by '-5'.
c = -0.8

Simplifying
c = -0.8
Subproblem 2
Set the factor '(5 + -3c)' equal to zero and attempt to solve:

Simplifying
5 + -3c = 0

Solving
5 + -3c = 0

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

Add '-5' to each side of the equation.
5 + -5 + -3c = 0 + -5

Combine like terms: 5 + -5 = 0
0 + -3c = 0 + -5
-3c = 0 + -5

Combine like terms: 0 + -5 = -5
-3c = -5

Divide each side by '-3'.
c = 1.666666667

Simplifying
c = 1.666666667
Solution
c = {-0.8, 1.666666667}