0=x^2-8x-13

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Solution for 0=x^2-8x-13 equation:


Simplifying
0 = x2 + -8x + -13

Reorder the terms:
0 = -13 + -8x + x2

Solving
0 = -13 + -8x + x2

Solving for variable 'x'.

Combine like terms: 0 + 13 = 13
13 + 8x + -1x2 = -13 + -8x + x2 + 13 + 8x + -1x2

Reorder the terms:
13 + 8x + -1x2 = -13 + 13 + -8x + 8x + x2 + -1x2

Combine like terms: -13 + 13 = 0
13 + 8x + -1x2 = 0 + -8x + 8x + x2 + -1x2
13 + 8x + -1x2 = -8x + 8x + x2 + -1x2

Combine like terms: -8x + 8x = 0
13 + 8x + -1x2 = 0 + x2 + -1x2
13 + 8x + -1x2 = x2 + -1x2

Combine like terms: x2 + -1x2 = 0
13 + 8x + -1x2 = 0

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

Divide each side by '-1'.
-13 + -8x + x2 = 0

Move the constant term to the right:

Add '13' to each side of the equation.
-13 + -8x + 13 + x2 = 0 + 13

Reorder the terms:
-13 + 13 + -8x + x2 = 0 + 13

Combine like terms: -13 + 13 = 0
0 + -8x + x2 = 0 + 13
-8x + x2 = 0 + 13

Combine like terms: 0 + 13 = 13
-8x + x2 = 13

The x term is -8x.  Take half its coefficient (-4).
Square it (16) and add it to both sides.

Add '16' to each side of the equation.
-8x + 16 + x2 = 13 + 16

Reorder the terms:
16 + -8x + x2 = 13 + 16

Combine like terms: 13 + 16 = 29
16 + -8x + x2 = 29

Factor a perfect square on the left side:
(x + -4)(x + -4) = 29

Calculate the square root of the right side: 5.385164807

Break this problem into two subproblems by setting 
(x + -4) equal to 5.385164807 and -5.385164807.

Subproblem 1

x + -4 = 5.385164807 Simplifying x + -4 = 5.385164807 Reorder the terms: -4 + x = 5.385164807 Solving -4 + x = 5.385164807 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '4' to each side of the equation. -4 + 4 + x = 5.385164807 + 4 Combine like terms: -4 + 4 = 0 0 + x = 5.385164807 + 4 x = 5.385164807 + 4 Combine like terms: 5.385164807 + 4 = 9.385164807 x = 9.385164807 Simplifying x = 9.385164807

Subproblem 2

x + -4 = -5.385164807 Simplifying x + -4 = -5.385164807 Reorder the terms: -4 + x = -5.385164807 Solving -4 + x = -5.385164807 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '4' to each side of the equation. -4 + 4 + x = -5.385164807 + 4 Combine like terms: -4 + 4 = 0 0 + x = -5.385164807 + 4 x = -5.385164807 + 4 Combine like terms: -5.385164807 + 4 = -1.385164807 x = -1.385164807 Simplifying x = -1.385164807

Solution

The solution to the problem is based on the solutions from the subproblems. x = {9.385164807, -1.385164807}

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