-b^2=9b-20

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Solution for -b^2=9b-20 equation:


Simplifying
-1b2 = 9b + -20

Reorder the terms:
-1b2 = -20 + 9b

Solving
-1b2 = -20 + 9b

Solving for variable 'b'.

Reorder the terms:
20 + -9b + -1b2 = -20 + 9b + 20 + -9b

Reorder the terms:
20 + -9b + -1b2 = -20 + 20 + 9b + -9b

Combine like terms: -20 + 20 = 0
20 + -9b + -1b2 = 0 + 9b + -9b
20 + -9b + -1b2 = 9b + -9b

Combine like terms: 9b + -9b = 0
20 + -9b + -1b2 = 0

Begin completing the square.  Divide all terms by
-1 the coefficient of the squared term: 

Divide each side by '-1'.
-20 + 9b + b2 = 0

Move the constant term to the right:

Add '20' to each side of the equation.
-20 + 9b + 20 + b2 = 0 + 20

Reorder the terms:
-20 + 20 + 9b + b2 = 0 + 20

Combine like terms: -20 + 20 = 0
0 + 9b + b2 = 0 + 20
9b + b2 = 0 + 20

Combine like terms: 0 + 20 = 20
9b + b2 = 20

The b term is 9b.  Take half its coefficient (4.5).
Square it (20.25) and add it to both sides.

Add '20.25' to each side of the equation.
9b + 20.25 + b2 = 20 + 20.25

Reorder the terms:
20.25 + 9b + b2 = 20 + 20.25

Combine like terms: 20 + 20.25 = 40.25
20.25 + 9b + b2 = 40.25

Factor a perfect square on the left side:
(b + 4.5)(b + 4.5) = 40.25

Calculate the square root of the right side: 6.34428877

Break this problem into two subproblems by setting 
(b + 4.5) equal to 6.34428877 and -6.34428877.

Subproblem 1

b + 4.5 = 6.34428877 Simplifying b + 4.5 = 6.34428877 Reorder the terms: 4.5 + b = 6.34428877 Solving 4.5 + b = 6.34428877 Solving for variable 'b'. Move all terms containing b to the left, all other terms to the right. Add '-4.5' to each side of the equation. 4.5 + -4.5 + b = 6.34428877 + -4.5 Combine like terms: 4.5 + -4.5 = 0.0 0.0 + b = 6.34428877 + -4.5 b = 6.34428877 + -4.5 Combine like terms: 6.34428877 + -4.5 = 1.84428877 b = 1.84428877 Simplifying b = 1.84428877

Subproblem 2

b + 4.5 = -6.34428877 Simplifying b + 4.5 = -6.34428877 Reorder the terms: 4.5 + b = -6.34428877 Solving 4.5 + b = -6.34428877 Solving for variable 'b'. Move all terms containing b to the left, all other terms to the right. Add '-4.5' to each side of the equation. 4.5 + -4.5 + b = -6.34428877 + -4.5 Combine like terms: 4.5 + -4.5 = 0.0 0.0 + b = -6.34428877 + -4.5 b = -6.34428877 + -4.5 Combine like terms: -6.34428877 + -4.5 = -10.84428877 b = -10.84428877 Simplifying b = -10.84428877

Solution

The solution to the problem is based on the solutions from the subproblems. b = {1.84428877, -10.84428877}

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