x^2-8x-71=0

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Solution for x^2-8x-71=0 equation:


Simplifying
x2 + -8x + -71 = 0

Reorder the terms:
-71 + -8x + x2 = 0

Solving
-71 + -8x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '71' to each side of the equation.
-71 + -8x + 71 + x2 = 0 + 71

Reorder the terms:
-71 + 71 + -8x + x2 = 0 + 71

Combine like terms: -71 + 71 = 0
0 + -8x + x2 = 0 + 71
-8x + x2 = 0 + 71

Combine like terms: 0 + 71 = 71
-8x + x2 = 71

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 = 71 + 16

Reorder the terms:
16 + -8x + x2 = 71 + 16

Combine like terms: 71 + 16 = 87
16 + -8x + x2 = 87

Factor a perfect square on the left side:
(x + -4)(x + -4) = 87

Calculate the square root of the right side: 9.327379053

Break this problem into two subproblems by setting 
(x + -4) equal to 9.327379053 and -9.327379053.

Subproblem 1

x + -4 = 9.327379053 Simplifying x + -4 = 9.327379053 Reorder the terms: -4 + x = 9.327379053 Solving -4 + x = 9.327379053 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 = 9.327379053 + 4 Combine like terms: -4 + 4 = 0 0 + x = 9.327379053 + 4 x = 9.327379053 + 4 Combine like terms: 9.327379053 + 4 = 13.327379053 x = 13.327379053 Simplifying x = 13.327379053

Subproblem 2

x + -4 = -9.327379053 Simplifying x + -4 = -9.327379053 Reorder the terms: -4 + x = -9.327379053 Solving -4 + x = -9.327379053 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 = -9.327379053 + 4 Combine like terms: -4 + 4 = 0 0 + x = -9.327379053 + 4 x = -9.327379053 + 4 Combine like terms: -9.327379053 + 4 = -5.327379053 x = -5.327379053 Simplifying x = -5.327379053

Solution

The solution to the problem is based on the solutions from the subproblems. x = {13.327379053, -5.327379053}

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