15x^2+40x=168

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Solution for 15x^2+40x=168 equation:


Simplifying
15x2 + 40x = 168

Reorder the terms:
40x + 15x2 = 168

Solving
40x + 15x2 = 168

Solving for variable 'x'.

Reorder the terms:
-168 + 40x + 15x2 = 168 + -168

Combine like terms: 168 + -168 = 0
-168 + 40x + 15x2 = 0

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

Divide each side by '15'.
-11.2 + 2.666666667x + x2 = 0

Move the constant term to the right:

Add '11.2' to each side of the equation.
-11.2 + 2.666666667x + 11.2 + x2 = 0 + 11.2

Reorder the terms:
-11.2 + 11.2 + 2.666666667x + x2 = 0 + 11.2

Combine like terms: -11.2 + 11.2 = 0.0
0.0 + 2.666666667x + x2 = 0 + 11.2
2.666666667x + x2 = 0 + 11.2

Combine like terms: 0 + 11.2 = 11.2
2.666666667x + x2 = 11.2

The x term is 2.666666667x.  Take half its coefficient (1.333333334).
Square it (1.777777780) and add it to both sides.

Add '1.777777780' to each side of the equation.
2.666666667x + 1.777777780 + x2 = 11.2 + 1.777777780

Reorder the terms:
1.777777780 + 2.666666667x + x2 = 11.2 + 1.777777780

Combine like terms: 11.2 + 1.777777780 = 12.97777778
1.777777780 + 2.666666667x + x2 = 12.97777778

Factor a perfect square on the left side:
(x + 1.333333334)(x + 1.333333334) = 12.97777778

Calculate the square root of the right side: 3.60246829

Break this problem into two subproblems by setting 
(x + 1.333333334) equal to 3.60246829 and -3.60246829.

Subproblem 1

x + 1.333333334 = 3.60246829 Simplifying x + 1.333333334 = 3.60246829 Reorder the terms: 1.333333334 + x = 3.60246829 Solving 1.333333334 + x = 3.60246829 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.333333334' to each side of the equation. 1.333333334 + -1.333333334 + x = 3.60246829 + -1.333333334 Combine like terms: 1.333333334 + -1.333333334 = 0.000000000 0.000000000 + x = 3.60246829 + -1.333333334 x = 3.60246829 + -1.333333334 Combine like terms: 3.60246829 + -1.333333334 = 2.269134956 x = 2.269134956 Simplifying x = 2.269134956

Subproblem 2

x + 1.333333334 = -3.60246829 Simplifying x + 1.333333334 = -3.60246829 Reorder the terms: 1.333333334 + x = -3.60246829 Solving 1.333333334 + x = -3.60246829 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.333333334' to each side of the equation. 1.333333334 + -1.333333334 + x = -3.60246829 + -1.333333334 Combine like terms: 1.333333334 + -1.333333334 = 0.000000000 0.000000000 + x = -3.60246829 + -1.333333334 x = -3.60246829 + -1.333333334 Combine like terms: -3.60246829 + -1.333333334 = -4.935801624 x = -4.935801624 Simplifying x = -4.935801624

Solution

The solution to the problem is based on the solutions from the subproblems. x = {2.269134956, -4.935801624}

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