21x^2+13x=8

Solution for 21x^2+13x=8 equation:

Simplifying
21x2 + 13x = 8

Reorder the terms:
13x + 21x2 = 8

Solving
13x + 21x2 = 8

Solving for variable 'x'.

Reorder the terms:
-8 + 13x + 21x2 = 8 + -8

Combine like terms: 8 + -8 = 0
-8 + 13x + 21x2 = 0

Factor a trinomial.
(-1 + -1x)(8 + -21x) = 0

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

Simplifying
-1 + -1x = 0

Solving
-1 + -1x = 0

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

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

Combine like terms: -1 + 1 = 0
0 + -1x = 0 + 1
-1x = 0 + 1

Combine like terms: 0 + 1 = 1
-1x = 1

Divide each side by '-1'.
x = -1

Simplifying
x = -1
Subproblem 2
Set the factor '(8 + -21x)' equal to zero and attempt to solve:

Simplifying
8 + -21x = 0

Solving
8 + -21x = 0

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

Add '-8' to each side of the equation.
8 + -8 + -21x = 0 + -8

Combine like terms: 8 + -8 = 0
0 + -21x = 0 + -8
-21x = 0 + -8

Combine like terms: 0 + -8 = -8
-21x = -8

Divide each side by '-21'.
x = 0.380952381

Simplifying
x = 0.380952381
Solution
x = {-1, 0.380952381}