4b^2-21=25b

Solution for 4b^2-21=25b equation:

Simplifying
4b2 + -21 = 25b

Reorder the terms:
-21 + 4b2 = 25b

Solving
-21 + 4b2 = 25b

Solving for variable 'b'.

Reorder the terms:
-21 + -25b + 4b2 = 25b + -25b

Combine like terms: 25b + -25b = 0
-21 + -25b + 4b2 = 0

Factor a trinomial.
(-3 + -4b)(7 + -1b) = 0

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

Simplifying
-3 + -4b = 0

Solving
-3 + -4b = 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 + -4b = 0 + 3

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

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

Divide each side by '-4'.
b = -0.75

Simplifying
b = -0.75
Subproblem 2
Set the factor '(7 + -1b)' equal to zero and attempt to solve:

Simplifying
7 + -1b = 0

Solving
7 + -1b = 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 + -1b = 0 + -7

Combine like terms: 7 + -7 = 0
0 + -1b = 0 + -7
-1b = 0 + -7

Combine like terms: 0 + -7 = -7
-1b = -7

Divide each side by '-1'.
b = 7

Simplifying
b = 7
Solution
b = {-0.75, 7}