15x^2+70x-81=0

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Solution for 15x^2+70x-81=0 equation:


Simplifying
15x2 + 70x + -81 = 0

Reorder the terms:
-81 + 70x + 15x2 = 0

Solving
-81 + 70x + 15x2 = 0

Solving for variable 'x'.

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

Divide each side by '15'.
-5.4 + 4.666666667x + x2 = 0

Move the constant term to the right:

Add '5.4' to each side of the equation.
-5.4 + 4.666666667x + 5.4 + x2 = 0 + 5.4

Reorder the terms:
-5.4 + 5.4 + 4.666666667x + x2 = 0 + 5.4

Combine like terms: -5.4 + 5.4 = 0.0
0.0 + 4.666666667x + x2 = 0 + 5.4
4.666666667x + x2 = 0 + 5.4

Combine like terms: 0 + 5.4 = 5.4
4.666666667x + x2 = 5.4

The x term is 4.666666667x.  Take half its coefficient (2.333333334).
Square it (5.444444448) and add it to both sides.

Add '5.444444448' to each side of the equation.
4.666666667x + 5.444444448 + x2 = 5.4 + 5.444444448

Reorder the terms:
5.444444448 + 4.666666667x + x2 = 5.4 + 5.444444448

Combine like terms: 5.4 + 5.444444448 = 10.844444448
5.444444448 + 4.666666667x + x2 = 10.844444448

Factor a perfect square on the left side:
(x + 2.333333334)(x + 2.333333334) = 10.844444448

Calculate the square root of the right side: 3.29309041

Break this problem into two subproblems by setting 
(x + 2.333333334) equal to 3.29309041 and -3.29309041.

Subproblem 1

x + 2.333333334 = 3.29309041 Simplifying x + 2.333333334 = 3.29309041 Reorder the terms: 2.333333334 + x = 3.29309041 Solving 2.333333334 + x = 3.29309041 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-2.333333334' to each side of the equation. 2.333333334 + -2.333333334 + x = 3.29309041 + -2.333333334 Combine like terms: 2.333333334 + -2.333333334 = 0.000000000 0.000000000 + x = 3.29309041 + -2.333333334 x = 3.29309041 + -2.333333334 Combine like terms: 3.29309041 + -2.333333334 = 0.959757076 x = 0.959757076 Simplifying x = 0.959757076

Subproblem 2

x + 2.333333334 = -3.29309041 Simplifying x + 2.333333334 = -3.29309041 Reorder the terms: 2.333333334 + x = -3.29309041 Solving 2.333333334 + x = -3.29309041 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-2.333333334' to each side of the equation. 2.333333334 + -2.333333334 + x = -3.29309041 + -2.333333334 Combine like terms: 2.333333334 + -2.333333334 = 0.000000000 0.000000000 + x = -3.29309041 + -2.333333334 x = -3.29309041 + -2.333333334 Combine like terms: -3.29309041 + -2.333333334 = -5.626423744 x = -5.626423744 Simplifying x = -5.626423744

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.959757076, -5.626423744}

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