21b^2-6b-15=0

Solution for 21b^2-6b-15=0 equation:

Simplifying
21b2 + -6b + -15 = 0

Reorder the terms:
-15 + -6b + 21b2 = 0

Solving
-15 + -6b + 21b2 = 0

Solving for variable 'b'.

Factor out the Greatest Common Factor (GCF), '3'.
3(-5 + -2b + 7b2) = 0

Factor a trinomial.
3((-5 + -7b)(1 + -1b)) = 0

Ignore the factor 3.
Subproblem 1
Set the factor '(-5 + -7b)' equal to zero and attempt to solve:

Simplifying
-5 + -7b = 0

Solving
-5 + -7b = 0

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

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

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

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

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

Simplifying
b = -0.7142857143
Subproblem 2
Set the factor '(1 + -1b)' equal to zero and attempt to solve:

Simplifying
1 + -1b = 0

Solving
1 + -1b = 0

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

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

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

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

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

Simplifying
b = 1
Solution
b = {-0.7142857143, 1}