3x^2+15x-6.9=0

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Solution for 3x^2+15x-6.9=0 equation:


Simplifying
3x2 + 15x + -6.9 = 0

Reorder the terms:
-6.9 + 15x + 3x2 = 0

Solving
-6.9 + 15x + 3x2 = 0

Solving for variable 'x'.

Begin completing the square.  Divide all terms by
3 the coefficient of the squared term: 

Divide each side by '3'.
-2.3 + 5x + x2 = 0

Move the constant term to the right:

Add '2.3' to each side of the equation.
-2.3 + 5x + 2.3 + x2 = 0 + 2.3

Reorder the terms:
-2.3 + 2.3 + 5x + x2 = 0 + 2.3

Combine like terms: -2.3 + 2.3 = 0.0
0.0 + 5x + x2 = 0 + 2.3
5x + x2 = 0 + 2.3

Combine like terms: 0 + 2.3 = 2.3
5x + x2 = 2.3

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 = 2.3 + 6.25

Reorder the terms:
6.25 + 5x + x2 = 2.3 + 6.25

Combine like terms: 2.3 + 6.25 = 8.55
6.25 + 5x + x2 = 8.55

Factor a perfect square on the left side:
(x + 2.5)(x + 2.5) = 8.55

Calculate the square root of the right side: 2.924038303

Break this problem into two subproblems by setting 
(x + 2.5) equal to 2.924038303 and -2.924038303.

Subproblem 1

x + 2.5 = 2.924038303 Simplifying x + 2.5 = 2.924038303 Reorder the terms: 2.5 + x = 2.924038303 Solving 2.5 + x = 2.924038303 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 = 2.924038303 + -2.5 Combine like terms: 2.5 + -2.5 = 0.0 0.0 + x = 2.924038303 + -2.5 x = 2.924038303 + -2.5 Combine like terms: 2.924038303 + -2.5 = 0.424038303 x = 0.424038303 Simplifying x = 0.424038303

Subproblem 2

x + 2.5 = -2.924038303 Simplifying x + 2.5 = -2.924038303 Reorder the terms: 2.5 + x = -2.924038303 Solving 2.5 + x = -2.924038303 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 = -2.924038303 + -2.5 Combine like terms: 2.5 + -2.5 = 0.0 0.0 + x = -2.924038303 + -2.5 x = -2.924038303 + -2.5 Combine like terms: -2.924038303 + -2.5 = -5.424038303 x = -5.424038303 Simplifying x = -5.424038303

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.424038303, -5.424038303}

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