x^2-8x-18=9

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Solution for x^2-8x-18=9 equation:


Simplifying
x2 + -8x + -18 = 9

Reorder the terms:
-18 + -8x + x2 = 9

Solving
-18 + -8x + x2 = 9

Solving for variable 'x'.

Reorder the terms:
-18 + -9 + -8x + x2 = 9 + -9

Combine like terms: -18 + -9 = -27
-27 + -8x + x2 = 9 + -9

Combine like terms: 9 + -9 = 0
-27 + -8x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '27' to each side of the equation.
-27 + -8x + 27 + x2 = 0 + 27

Reorder the terms:
-27 + 27 + -8x + x2 = 0 + 27

Combine like terms: -27 + 27 = 0
0 + -8x + x2 = 0 + 27
-8x + x2 = 0 + 27

Combine like terms: 0 + 27 = 27
-8x + x2 = 27

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 = 27 + 16

Reorder the terms:
16 + -8x + x2 = 27 + 16

Combine like terms: 27 + 16 = 43
16 + -8x + x2 = 43

Factor a perfect square on the left side:
(x + -4)(x + -4) = 43

Calculate the square root of the right side: 6.557438524

Break this problem into two subproblems by setting 
(x + -4) equal to 6.557438524 and -6.557438524.

Subproblem 1

x + -4 = 6.557438524 Simplifying x + -4 = 6.557438524 Reorder the terms: -4 + x = 6.557438524 Solving -4 + x = 6.557438524 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 = 6.557438524 + 4 Combine like terms: -4 + 4 = 0 0 + x = 6.557438524 + 4 x = 6.557438524 + 4 Combine like terms: 6.557438524 + 4 = 10.557438524 x = 10.557438524 Simplifying x = 10.557438524

Subproblem 2

x + -4 = -6.557438524 Simplifying x + -4 = -6.557438524 Reorder the terms: -4 + x = -6.557438524 Solving -4 + x = -6.557438524 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 = -6.557438524 + 4 Combine like terms: -4 + 4 = 0 0 + x = -6.557438524 + 4 x = -6.557438524 + 4 Combine like terms: -6.557438524 + 4 = -2.557438524 x = -2.557438524 Simplifying x = -2.557438524

Solution

The solution to the problem is based on the solutions from the subproblems. x = {10.557438524, -2.557438524}

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