x(x-9)=20

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Solution for x(x-9)=20 equation: 


Simplifying
x(x + -9) = 20

Reorder the terms:
x(-9 + x) = 20
(-9 * x + x * x) = 20
(-9x + x2) = 20

Solving
-9x + x2 = 20

Solving for variable 'x'.

Reorder the terms:
-20 + -9x + x2 = 20 + -20

Combine like terms: 20 + -20 = 0
-20 + -9x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '20' to each side of the equation.
-20 + -9x + 20 + x2 = 0 + 20

Reorder the terms:
-20 + 20 + -9x + x2 = 0 + 20

Combine like terms: -20 + 20 = 0
0 + -9x + x2 = 0 + 20
-9x + x2 = 0 + 20

Combine like terms: 0 + 20 = 20
-9x + x2 = 20

The x term is -9x.  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.
-9x + 20.25 + x2 = 20 + 20.25

Reorder the terms:
20.25 + -9x + x2 = 20 + 20.25

Combine like terms: 20 + 20.25 = 40.25
20.25 + -9x + x2 = 40.25

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

Calculate the square root of the right side: 6.34428877

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


Subproblem 1
x + -4.5 = 6.34428877

Simplifying
x + -4.5 = 6.34428877

Reorder the terms:
-4.5 + x = 6.34428877

Solving
-4.5 + x = 6.34428877

Solving for variable 'x'.

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

Add '4.5' to each side of the equation.
-4.5 + 4.5 + x = 6.34428877 + 4.5

Combine like terms: -4.5 + 4.5 = 0.0
0.0 + x = 6.34428877 + 4.5
x = 6.34428877 + 4.5

Combine like terms: 6.34428877 + 4.5 = 10.84428877
x = 10.84428877

Simplifying
x = 10.84428877


Subproblem 2
x + -4.5 = -6.34428877

Simplifying
x + -4.5 = -6.34428877

Reorder the terms:
-4.5 + x = -6.34428877

Solving
-4.5 + x = -6.34428877

Solving for variable 'x'.

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

Add '4.5' to each side of the equation.
-4.5 + 4.5 + x = -6.34428877 + 4.5

Combine like terms: -4.5 + 4.5 = 0.0
0.0 + x = -6.34428877 + 4.5
x = -6.34428877 + 4.5

Combine like terms: -6.34428877 + 4.5 = -1.84428877
x = -1.84428877

Simplifying
x = -1.84428877


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

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