21n^2+13n-20=0

Solution for 21n^2+13n-20=0 equation:

Simplifying
21n2 + 13n + -20 = 0

Reorder the terms:
-20 + 13n + 21n2 = 0

Solving
-20 + 13n + 21n2 = 0

Solving for variable 'n'.

Factor a trinomial.
(-4 + -3n)(5 + -7n) = 0

Subproblem 1
Set the factor '(-4 + -3n)' equal to zero and attempt to solve:

Simplifying
-4 + -3n = 0

Solving
-4 + -3n = 0

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

Add '4' to each side of the equation.
-4 + 4 + -3n = 0 + 4

Combine like terms: -4 + 4 = 0
0 + -3n = 0 + 4
-3n = 0 + 4

Combine like terms: 0 + 4 = 4
-3n = 4

Divide each side by '-3'.
n = -1.333333333

Simplifying
n = -1.333333333
Subproblem 2
Set the factor '(5 + -7n)' equal to zero and attempt to solve:

Simplifying
5 + -7n = 0

Solving
5 + -7n = 0

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

Add '-5' to each side of the equation.
5 + -5 + -7n = 0 + -5

Combine like terms: 5 + -5 = 0
0 + -7n = 0 + -5
-7n = 0 + -5

Combine like terms: 0 + -5 = -5
-7n = -5

Divide each side by '-7'.
n = 0.7142857143

Simplifying
n = 0.7142857143
Solution
n = {-1.333333333, 0.7142857143}