3x^2+4x=390

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Solution for 3x^2+4x=390 equation:


Simplifying
3x2 + 4x = 390

Reorder the terms:
4x + 3x2 = 390

Solving
4x + 3x2 = 390

Solving for variable 'x'.

Reorder the terms:
-390 + 4x + 3x2 = 390 + -390

Combine like terms: 390 + -390 = 0
-390 + 4x + 3x2 = 0

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

Divide each side by '3'.
-130 + 1.333333333x + x2 = 0

Move the constant term to the right:

Add '130' to each side of the equation.
-130 + 1.333333333x + 130 + x2 = 0 + 130

Reorder the terms:
-130 + 130 + 1.333333333x + x2 = 0 + 130

Combine like terms: -130 + 130 = 0
0 + 1.333333333x + x2 = 0 + 130
1.333333333x + x2 = 0 + 130

Combine like terms: 0 + 130 = 130
1.333333333x + x2 = 130

The x term is 1.333333333x.  Take half its coefficient (0.6666666665).
Square it (0.4444444442) and add it to both sides.

Add '0.4444444442' to each side of the equation.
1.333333333x + 0.4444444442 + x2 = 130 + 0.4444444442

Reorder the terms:
0.4444444442 + 1.333333333x + x2 = 130 + 0.4444444442

Combine like terms: 130 + 0.4444444442 = 130.4444444442
0.4444444442 + 1.333333333x + x2 = 130.4444444442

Factor a perfect square on the left side:
(x + 0.6666666665)(x + 0.6666666665) = 130.4444444442

Calculate the square root of the right side: 11.421227799

Break this problem into two subproblems by setting 
(x + 0.6666666665) equal to 11.421227799 and -11.421227799.

Subproblem 1

x + 0.6666666665 = 11.421227799 Simplifying x + 0.6666666665 = 11.421227799 Reorder the terms: 0.6666666665 + x = 11.421227799 Solving 0.6666666665 + x = 11.421227799 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.6666666665' to each side of the equation. 0.6666666665 + -0.6666666665 + x = 11.421227799 + -0.6666666665 Combine like terms: 0.6666666665 + -0.6666666665 = 0.0000000000 0.0000000000 + x = 11.421227799 + -0.6666666665 x = 11.421227799 + -0.6666666665 Combine like terms: 11.421227799 + -0.6666666665 = 10.7545611325 x = 10.7545611325 Simplifying x = 10.7545611325

Subproblem 2

x + 0.6666666665 = -11.421227799 Simplifying x + 0.6666666665 = -11.421227799 Reorder the terms: 0.6666666665 + x = -11.421227799 Solving 0.6666666665 + x = -11.421227799 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.6666666665' to each side of the equation. 0.6666666665 + -0.6666666665 + x = -11.421227799 + -0.6666666665 Combine like terms: 0.6666666665 + -0.6666666665 = 0.0000000000 0.0000000000 + x = -11.421227799 + -0.6666666665 x = -11.421227799 + -0.6666666665 Combine like terms: -11.421227799 + -0.6666666665 = -12.0878944655 x = -12.0878944655 Simplifying x = -12.0878944655

Solution

The solution to the problem is based on the solutions from the subproblems. x = {10.7545611325, -12.0878944655}

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