x^2-1=8x

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Solution for x^2-1=8x equation:


Simplifying
x2 + -1 = 8x

Reorder the terms:
-1 + x2 = 8x

Solving
-1 + x2 = 8x

Solving for variable 'x'.

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

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

Begin completing the square.

Move the constant term to the right:

Add '1' to each side of the equation.
-1 + -8x + 1 + x2 = 0 + 1

Reorder the terms:
-1 + 1 + -8x + x2 = 0 + 1

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

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

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 = 1 + 16

Reorder the terms:
16 + -8x + x2 = 1 + 16

Combine like terms: 1 + 16 = 17
16 + -8x + x2 = 17

Factor a perfect square on the left side:
(x + -4)(x + -4) = 17

Calculate the square root of the right side: 4.123105626

Break this problem into two subproblems by setting 
(x + -4) equal to 4.123105626 and -4.123105626.

Subproblem 1

x + -4 = 4.123105626 Simplifying x + -4 = 4.123105626 Reorder the terms: -4 + x = 4.123105626 Solving -4 + x = 4.123105626 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 = 4.123105626 + 4 Combine like terms: -4 + 4 = 0 0 + x = 4.123105626 + 4 x = 4.123105626 + 4 Combine like terms: 4.123105626 + 4 = 8.123105626 x = 8.123105626 Simplifying x = 8.123105626

Subproblem 2

x + -4 = -4.123105626 Simplifying x + -4 = -4.123105626 Reorder the terms: -4 + x = -4.123105626 Solving -4 + x = -4.123105626 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 = -4.123105626 + 4 Combine like terms: -4 + 4 = 0 0 + x = -4.123105626 + 4 x = -4.123105626 + 4 Combine like terms: -4.123105626 + 4 = -0.123105626 x = -0.123105626 Simplifying x = -0.123105626

Solution

The solution to the problem is based on the solutions from the subproblems. x = {8.123105626, -0.123105626}

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