15c^2-26c-21=0

Solution for 15c^2-26c-21=0 equation:

Simplifying
15c2 + -26c + -21 = 0

Reorder the terms:
-21 + -26c + 15c2 = 0

Solving
-21 + -26c + 15c2 = 0

Solving for variable 'c'.

Factor a trinomial.
(-3 + -5c)(7 + -3c) = 0

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

Simplifying
-3 + -5c = 0

Solving
-3 + -5c = 0

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

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

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

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

Divide each side by '-5'.
c = -0.6

Simplifying
c = -0.6
Subproblem 2
Set the factor '(7 + -3c)' equal to zero and attempt to solve:

Simplifying
7 + -3c = 0

Solving
7 + -3c = 0

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

Add '-7' to each side of the equation.
7 + -7 + -3c = 0 + -7

Combine like terms: 7 + -7 = 0
0 + -3c = 0 + -7
-3c = 0 + -7

Combine like terms: 0 + -7 = -7
-3c = -7

Divide each side by '-3'.
c = 2.333333333

Simplifying
c = 2.333333333
Solution
c = {-0.6, 2.333333333}