x^2+15x=-16

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Solution for x^2+15x=-16 equation:


Simplifying
x2 + 15x = -16

Reorder the terms:
15x + x2 = -16

Solving
15x + x2 = -16

Solving for variable 'x'.

Reorder the terms:
16 + 15x + x2 = -16 + 16

Combine like terms: -16 + 16 = 0
16 + 15x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '-16' to each side of the equation.
16 + 15x + -16 + x2 = 0 + -16

Reorder the terms:
16 + -16 + 15x + x2 = 0 + -16

Combine like terms: 16 + -16 = 0
0 + 15x + x2 = 0 + -16
15x + x2 = 0 + -16

Combine like terms: 0 + -16 = -16
15x + x2 = -16

The x term is 15x.  Take half its coefficient (7.5).
Square it (56.25) and add it to both sides.

Add '56.25' to each side of the equation.
15x + 56.25 + x2 = -16 + 56.25

Reorder the terms:
56.25 + 15x + x2 = -16 + 56.25

Combine like terms: -16 + 56.25 = 40.25
56.25 + 15x + x2 = 40.25

Factor a perfect square on the left side:
(x + 7.5)(x + 7.5) = 40.25

Calculate the square root of the right side: 6.34428877

Break this problem into two subproblems by setting 
(x + 7.5) equal to 6.34428877 and -6.34428877.

Subproblem 1

x + 7.5 = 6.34428877 Simplifying x + 7.5 = 6.34428877 Reorder the terms: 7.5 + x = 6.34428877 Solving 7.5 + x = 6.34428877 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-7.5' to each side of the equation. 7.5 + -7.5 + x = 6.34428877 + -7.5 Combine like terms: 7.5 + -7.5 = 0.0 0.0 + x = 6.34428877 + -7.5 x = 6.34428877 + -7.5 Combine like terms: 6.34428877 + -7.5 = -1.15571123 x = -1.15571123 Simplifying x = -1.15571123

Subproblem 2

x + 7.5 = -6.34428877 Simplifying x + 7.5 = -6.34428877 Reorder the terms: 7.5 + x = -6.34428877 Solving 7.5 + x = -6.34428877 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-7.5' to each side of the equation. 7.5 + -7.5 + x = -6.34428877 + -7.5 Combine like terms: 7.5 + -7.5 = 0.0 0.0 + x = -6.34428877 + -7.5 x = -6.34428877 + -7.5 Combine like terms: -6.34428877 + -7.5 = -13.84428877 x = -13.84428877 Simplifying x = -13.84428877

Solution

The solution to the problem is based on the solutions from the subproblems. x = {-1.15571123, -13.84428877}

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