2b^2+b-21=0

Solution for 2b^2+b-21=0 equation:

Simplifying
2b2 + b + -21 = 0

Reorder the terms:
-21 + b + 2b2 = 0

Solving
-21 + b + 2b2 = 0

Solving for variable 'b'.

Factor a trinomial.
(-7 + -2b)(3 + -1b) = 0

Subproblem 1
Set the factor '(-7 + -2b)' equal to zero and attempt to solve:

Simplifying
-7 + -2b = 0

Solving
-7 + -2b = 0

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

Add '7' to each side of the equation.
-7 + 7 + -2b = 0 + 7

Combine like terms: -7 + 7 = 0
0 + -2b = 0 + 7
-2b = 0 + 7

Combine like terms: 0 + 7 = 7
-2b = 7

Divide each side by '-2'.
b = -3.5

Simplifying
b = -3.5
Subproblem 2
Set the factor '(3 + -1b)' equal to zero and attempt to solve:

Simplifying
3 + -1b = 0

Solving
3 + -1b = 0

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

Add '-3' to each side of the equation.
3 + -3 + -1b = 0 + -3

Combine like terms: 3 + -3 = 0
0 + -1b = 0 + -3
-1b = 0 + -3

Combine like terms: 0 + -3 = -3
-1b = -3

Divide each side by '-1'.
b = 3

Simplifying
b = 3
Solution
b = {-3.5, 3}