x^2+15x+28=0

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Solution for x^2+15x+28=0 equation:


Simplifying
x2 + 15x + 28 = 0

Reorder the terms:
28 + 15x + x2 = 0

Solving
28 + 15x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '-28' to each side of the equation.
28 + 15x + -28 + x2 = 0 + -28

Reorder the terms:
28 + -28 + 15x + x2 = 0 + -28

Combine like terms: 28 + -28 = 0
0 + 15x + x2 = 0 + -28
15x + x2 = 0 + -28

Combine like terms: 0 + -28 = -28
15x + x2 = -28

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 = -28 + 56.25

Reorder the terms:
56.25 + 15x + x2 = -28 + 56.25

Combine like terms: -28 + 56.25 = 28.25
56.25 + 15x + x2 = 28.25

Factor a perfect square on the left side:
(x + 7.5)(x + 7.5) = 28.25

Calculate the square root of the right side: 5.315072906

Break this problem into two subproblems by setting 
(x + 7.5) equal to 5.315072906 and -5.315072906.

Subproblem 1

x + 7.5 = 5.315072906 Simplifying x + 7.5 = 5.315072906 Reorder the terms: 7.5 + x = 5.315072906 Solving 7.5 + x = 5.315072906 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 = 5.315072906 + -7.5 Combine like terms: 7.5 + -7.5 = 0.0 0.0 + x = 5.315072906 + -7.5 x = 5.315072906 + -7.5 Combine like terms: 5.315072906 + -7.5 = -2.184927094 x = -2.184927094 Simplifying x = -2.184927094

Subproblem 2

x + 7.5 = -5.315072906 Simplifying x + 7.5 = -5.315072906 Reorder the terms: 7.5 + x = -5.315072906 Solving 7.5 + x = -5.315072906 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 = -5.315072906 + -7.5 Combine like terms: 7.5 + -7.5 = 0.0 0.0 + x = -5.315072906 + -7.5 x = -5.315072906 + -7.5 Combine like terms: -5.315072906 + -7.5 = -12.815072906 x = -12.815072906 Simplifying x = -12.815072906

Solution

The solution to the problem is based on the solutions from the subproblems. x = {-2.184927094, -12.815072906}

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