x*x-8x-16=0

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Solution for x*x-8x-16=0 equation:


Simplifying
x * x + -8x + -16 = 0

Multiply x * x
x2 + -8x + -16 = 0

Reorder the terms:
-16 + -8x + x2 = 0

Solving
-16 + -8x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '16' to each side of the equation.
-16 + -8x + 16 + x2 = 0 + 16

Reorder the terms:
-16 + 16 + -8x + x2 = 0 + 16

Combine like terms: -16 + 16 = 0
0 + -8x + x2 = 0 + 16
-8x + x2 = 0 + 16

Combine like terms: 0 + 16 = 16
-8x + x2 = 16

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 = 16 + 16

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

Combine like terms: 16 + 16 = 32
16 + -8x + x2 = 32

Factor a perfect square on the left side:
(x + -4)(x + -4) = 32

Calculate the square root of the right side: 5.656854249

Break this problem into two subproblems by setting 
(x + -4) equal to 5.656854249 and -5.656854249.

Subproblem 1

x + -4 = 5.656854249 Simplifying x + -4 = 5.656854249 Reorder the terms: -4 + x = 5.656854249 Solving -4 + x = 5.656854249 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 = 5.656854249 + 4 Combine like terms: -4 + 4 = 0 0 + x = 5.656854249 + 4 x = 5.656854249 + 4 Combine like terms: 5.656854249 + 4 = 9.656854249 x = 9.656854249 Simplifying x = 9.656854249

Subproblem 2

x + -4 = -5.656854249 Simplifying x + -4 = -5.656854249 Reorder the terms: -4 + x = -5.656854249 Solving -4 + x = -5.656854249 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 = -5.656854249 + 4 Combine like terms: -4 + 4 = 0 0 + x = -5.656854249 + 4 x = -5.656854249 + 4 Combine like terms: -5.656854249 + 4 = -1.656854249 x = -1.656854249 Simplifying x = -1.656854249

Solution

The solution to the problem is based on the solutions from the subproblems. x = {9.656854249, -1.656854249}

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