x^2-x=15

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Solution for x^2-x=15 equation:


Simplifying
x2 + -1x = 15

Reorder the terms:
-1x + x2 = 15

Solving
-1x + x2 = 15

Solving for variable 'x'.

Reorder the terms:
-15 + -1x + x2 = 15 + -15

Combine like terms: 15 + -15 = 0
-15 + -1x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '15' to each side of the equation.
-15 + -1x + 15 + x2 = 0 + 15

Reorder the terms:
-15 + 15 + -1x + x2 = 0 + 15

Combine like terms: -15 + 15 = 0
0 + -1x + x2 = 0 + 15
-1x + x2 = 0 + 15

Combine like terms: 0 + 15 = 15
-1x + x2 = 15

The x term is -1x.  Take half its coefficient (-0.5).
Square it (0.25) and add it to both sides.

Add '0.25' to each side of the equation.
-1x + 0.25 + x2 = 15 + 0.25

Reorder the terms:
0.25 + -1x + x2 = 15 + 0.25

Combine like terms: 15 + 0.25 = 15.25
0.25 + -1x + x2 = 15.25

Factor a perfect square on the left side:
(x + -0.5)(x + -0.5) = 15.25

Calculate the square root of the right side: 3.905124838

Break this problem into two subproblems by setting 
(x + -0.5) equal to 3.905124838 and -3.905124838.

Subproblem 1

x + -0.5 = 3.905124838 Simplifying x + -0.5 = 3.905124838 Reorder the terms: -0.5 + x = 3.905124838 Solving -0.5 + x = 3.905124838 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.5' to each side of the equation. -0.5 + 0.5 + x = 3.905124838 + 0.5 Combine like terms: -0.5 + 0.5 = 0.0 0.0 + x = 3.905124838 + 0.5 x = 3.905124838 + 0.5 Combine like terms: 3.905124838 + 0.5 = 4.405124838 x = 4.405124838 Simplifying x = 4.405124838

Subproblem 2

x + -0.5 = -3.905124838 Simplifying x + -0.5 = -3.905124838 Reorder the terms: -0.5 + x = -3.905124838 Solving -0.5 + x = -3.905124838 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.5' to each side of the equation. -0.5 + 0.5 + x = -3.905124838 + 0.5 Combine like terms: -0.5 + 0.5 = 0.0 0.0 + x = -3.905124838 + 0.5 x = -3.905124838 + 0.5 Combine like terms: -3.905124838 + 0.5 = -3.405124838 x = -3.405124838 Simplifying x = -3.405124838

Solution

The solution to the problem is based on the solutions from the subproblems. x = {4.405124838, -3.405124838}

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