x^2-20x-18=7

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Solution for x^2-20x-18=7 equation:


Simplifying
x2 + -20x + -18 = 7

Reorder the terms:
-18 + -20x + x2 = 7

Solving
-18 + -20x + x2 = 7

Solving for variable 'x'.

Reorder the terms:
-18 + -7 + -20x + x2 = 7 + -7

Combine like terms: -18 + -7 = -25
-25 + -20x + x2 = 7 + -7

Combine like terms: 7 + -7 = 0
-25 + -20x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '25' to each side of the equation.
-25 + -20x + 25 + x2 = 0 + 25

Reorder the terms:
-25 + 25 + -20x + x2 = 0 + 25

Combine like terms: -25 + 25 = 0
0 + -20x + x2 = 0 + 25
-20x + x2 = 0 + 25

Combine like terms: 0 + 25 = 25
-20x + x2 = 25

The x term is -20x.  Take half its coefficient (-10).
Square it (100) and add it to both sides.

Add '100' to each side of the equation.
-20x + 100 + x2 = 25 + 100

Reorder the terms:
100 + -20x + x2 = 25 + 100

Combine like terms: 25 + 100 = 125
100 + -20x + x2 = 125

Factor a perfect square on the left side:
(x + -10)(x + -10) = 125

Calculate the square root of the right side: 11.180339887

Break this problem into two subproblems by setting 
(x + -10) equal to 11.180339887 and -11.180339887.

Subproblem 1

x + -10 = 11.180339887 Simplifying x + -10 = 11.180339887 Reorder the terms: -10 + x = 11.180339887 Solving -10 + x = 11.180339887 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '10' to each side of the equation. -10 + 10 + x = 11.180339887 + 10 Combine like terms: -10 + 10 = 0 0 + x = 11.180339887 + 10 x = 11.180339887 + 10 Combine like terms: 11.180339887 + 10 = 21.180339887 x = 21.180339887 Simplifying x = 21.180339887

Subproblem 2

x + -10 = -11.180339887 Simplifying x + -10 = -11.180339887 Reorder the terms: -10 + x = -11.180339887 Solving -10 + x = -11.180339887 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '10' to each side of the equation. -10 + 10 + x = -11.180339887 + 10 Combine like terms: -10 + 10 = 0 0 + x = -11.180339887 + 10 x = -11.180339887 + 10 Combine like terms: -11.180339887 + 10 = -1.180339887 x = -1.180339887 Simplifying x = -1.180339887

Solution

The solution to the problem is based on the solutions from the subproblems. x = {21.180339887, -1.180339887}

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