x^2-15=-5x

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Solution for x^2-15=-5x equation:


Simplifying
x2 + -15 = -5x

Reorder the terms:
-15 + x2 = -5x

Solving
-15 + x2 = -5x

Solving for variable 'x'.

Reorder the terms:
-15 + 5x + x2 = -5x + 5x

Combine like terms: -5x + 5x = 0
-15 + 5x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '15' to each side of the equation.
-15 + 5x + 15 + x2 = 0 + 15

Reorder the terms:
-15 + 15 + 5x + x2 = 0 + 15

Combine like terms: -15 + 15 = 0
0 + 5x + x2 = 0 + 15
5x + x2 = 0 + 15

Combine like terms: 0 + 15 = 15
5x + x2 = 15

The x term is 5x.  Take half its coefficient (2.5).
Square it (6.25) and add it to both sides.

Add '6.25' to each side of the equation.
5x + 6.25 + x2 = 15 + 6.25

Reorder the terms:
6.25 + 5x + x2 = 15 + 6.25

Combine like terms: 15 + 6.25 = 21.25
6.25 + 5x + x2 = 21.25

Factor a perfect square on the left side:
(x + 2.5)(x + 2.5) = 21.25

Calculate the square root of the right side: 4.609772229

Break this problem into two subproblems by setting 
(x + 2.5) equal to 4.609772229 and -4.609772229.

Subproblem 1

x + 2.5 = 4.609772229 Simplifying x + 2.5 = 4.609772229 Reorder the terms: 2.5 + x = 4.609772229 Solving 2.5 + x = 4.609772229 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-2.5' to each side of the equation. 2.5 + -2.5 + x = 4.609772229 + -2.5 Combine like terms: 2.5 + -2.5 = 0.0 0.0 + x = 4.609772229 + -2.5 x = 4.609772229 + -2.5 Combine like terms: 4.609772229 + -2.5 = 2.109772229 x = 2.109772229 Simplifying x = 2.109772229

Subproblem 2

x + 2.5 = -4.609772229 Simplifying x + 2.5 = -4.609772229 Reorder the terms: 2.5 + x = -4.609772229 Solving 2.5 + x = -4.609772229 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-2.5' to each side of the equation. 2.5 + -2.5 + x = -4.609772229 + -2.5 Combine like terms: 2.5 + -2.5 = 0.0 0.0 + x = -4.609772229 + -2.5 x = -4.609772229 + -2.5 Combine like terms: -4.609772229 + -2.5 = -7.109772229 x = -7.109772229 Simplifying x = -7.109772229

Solution

The solution to the problem is based on the solutions from the subproblems. x = {2.109772229, -7.109772229}

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