x^2+3x=39

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Solution for x^2+3x=39 equation:


Simplifying
x2 + 3x = 39

Reorder the terms:
3x + x2 = 39

Solving
3x + x2 = 39

Solving for variable 'x'.

Reorder the terms:
-39 + 3x + x2 = 39 + -39

Combine like terms: 39 + -39 = 0
-39 + 3x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '39' to each side of the equation.
-39 + 3x + 39 + x2 = 0 + 39

Reorder the terms:
-39 + 39 + 3x + x2 = 0 + 39

Combine like terms: -39 + 39 = 0
0 + 3x + x2 = 0 + 39
3x + x2 = 0 + 39

Combine like terms: 0 + 39 = 39
3x + x2 = 39

The x term is 3x.  Take half its coefficient (1.5).
Square it (2.25) and add it to both sides.

Add '2.25' to each side of the equation.
3x + 2.25 + x2 = 39 + 2.25

Reorder the terms:
2.25 + 3x + x2 = 39 + 2.25

Combine like terms: 39 + 2.25 = 41.25
2.25 + 3x + x2 = 41.25

Factor a perfect square on the left side:
(x + 1.5)(x + 1.5) = 41.25

Calculate the square root of the right side: 6.422616289

Break this problem into two subproblems by setting 
(x + 1.5) equal to 6.422616289 and -6.422616289.

Subproblem 1

x + 1.5 = 6.422616289 Simplifying x + 1.5 = 6.422616289 Reorder the terms: 1.5 + x = 6.422616289 Solving 1.5 + x = 6.422616289 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.5' to each side of the equation. 1.5 + -1.5 + x = 6.422616289 + -1.5 Combine like terms: 1.5 + -1.5 = 0.0 0.0 + x = 6.422616289 + -1.5 x = 6.422616289 + -1.5 Combine like terms: 6.422616289 + -1.5 = 4.922616289 x = 4.922616289 Simplifying x = 4.922616289

Subproblem 2

x + 1.5 = -6.422616289 Simplifying x + 1.5 = -6.422616289 Reorder the terms: 1.5 + x = -6.422616289 Solving 1.5 + x = -6.422616289 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.5' to each side of the equation. 1.5 + -1.5 + x = -6.422616289 + -1.5 Combine like terms: 1.5 + -1.5 = 0.0 0.0 + x = -6.422616289 + -1.5 x = -6.422616289 + -1.5 Combine like terms: -6.422616289 + -1.5 = -7.922616289 x = -7.922616289 Simplifying x = -7.922616289

Solution

The solution to the problem is based on the solutions from the subproblems. x = {4.922616289, -7.922616289}

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