x^2-4x-12.8=0

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Solution for x^2-4x-12.8=0 equation: 


Simplifying
x2 + -4x + -12.8 = 0

Reorder the terms:
-12.8 + -4x + x2 = 0

Solving
-12.8 + -4x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '12.8' to each side of the equation.
-12.8 + -4x + 12.8 + x2 = 0 + 12.8

Reorder the terms:
-12.8 + 12.8 + -4x + x2 = 0 + 12.8

Combine like terms: -12.8 + 12.8 = 0.0
0.0 + -4x + x2 = 0 + 12.8
-4x + x2 = 0 + 12.8

Combine like terms: 0 + 12.8 = 12.8
-4x + x2 = 12.8

The x term is -4x.  Take half its coefficient (-2).
Square it (4) and add it to both sides.

Add '4' to each side of the equation.
-4x + 4 + x2 = 12.8 + 4

Reorder the terms:
4 + -4x + x2 = 12.8 + 4

Combine like terms: 12.8 + 4 = 16.8
4 + -4x + x2 = 16.8

Factor a perfect square on the left side:
(x + -2)(x + -2) = 16.8

Calculate the square root of the right side: 4.098780306

Break this problem into two subproblems by setting 
(x + -2) equal to 4.098780306 and -4.098780306.


Subproblem 1
x + -2 = 4.098780306

Simplifying
x + -2 = 4.098780306

Reorder the terms:
-2 + x = 4.098780306

Solving
-2 + x = 4.098780306

Solving for variable 'x'.

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

Add '2' to each side of the equation.
-2 + 2 + x = 4.098780306 + 2

Combine like terms: -2 + 2 = 0
0 + x = 4.098780306 + 2
x = 4.098780306 + 2

Combine like terms: 4.098780306 + 2 = 6.098780306
x = 6.098780306

Simplifying
x = 6.098780306


Subproblem 2
x + -2 = -4.098780306

Simplifying
x + -2 = -4.098780306

Reorder the terms:
-2 + x = -4.098780306

Solving
-2 + x = -4.098780306

Solving for variable 'x'.

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

Add '2' to each side of the equation.
-2 + 2 + x = -4.098780306 + 2

Combine like terms: -2 + 2 = 0
0 + x = -4.098780306 + 2
x = -4.098780306 + 2

Combine like terms: -4.098780306 + 2 = -2.098780306
x = -2.098780306

Simplifying
x = -2.098780306


Solution
The solution to the problem is based on the solutions
from the subproblems.
x = {6.098780306, -2.098780306}

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