81x^2+72x+13=0

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Solution for 81x^2+72x+13=0 equation:


Simplifying
81x2 + 72x + 13 = 0

Reorder the terms:
13 + 72x + 81x2 = 0

Solving
13 + 72x + 81x2 = 0

Solving for variable 'x'.

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

Divide each side by '81'.
0.1604938272 + 0.8888888889x + x2 = 0

Move the constant term to the right:

Add '-0.1604938272' to each side of the equation.
0.1604938272 + 0.8888888889x + -0.1604938272 + x2 = 0 + -0.1604938272

Reorder the terms:
0.1604938272 + -0.1604938272 + 0.8888888889x + x2 = 0 + -0.1604938272

Combine like terms: 0.1604938272 + -0.1604938272 = 0.0000000000
0.0000000000 + 0.8888888889x + x2 = 0 + -0.1604938272
0.8888888889x + x2 = 0 + -0.1604938272

Combine like terms: 0 + -0.1604938272 = -0.1604938272
0.8888888889x + x2 = -0.1604938272

The x term is 0.8888888889x.  Take half its coefficient (0.4444444445).
Square it (0.1975308642) and add it to both sides.

Add '0.1975308642' to each side of the equation.
0.8888888889x + 0.1975308642 + x2 = -0.1604938272 + 0.1975308642

Reorder the terms:
0.1975308642 + 0.8888888889x + x2 = -0.1604938272 + 0.1975308642

Combine like terms: -0.1604938272 + 0.1975308642 = 0.037037037
0.1975308642 + 0.8888888889x + x2 = 0.037037037

Factor a perfect square on the left side:
(x + 0.4444444445)(x + 0.4444444445) = 0.037037037

Calculate the square root of the right side: 0.19245009

Break this problem into two subproblems by setting 
(x + 0.4444444445) equal to 0.19245009 and -0.19245009.

Subproblem 1

x + 0.4444444445 = 0.19245009 Simplifying x + 0.4444444445 = 0.19245009 Reorder the terms: 0.4444444445 + x = 0.19245009 Solving 0.4444444445 + x = 0.19245009 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.4444444445' to each side of the equation. 0.4444444445 + -0.4444444445 + x = 0.19245009 + -0.4444444445 Combine like terms: 0.4444444445 + -0.4444444445 = 0.0000000000 0.0000000000 + x = 0.19245009 + -0.4444444445 x = 0.19245009 + -0.4444444445 Combine like terms: 0.19245009 + -0.4444444445 = -0.2519943545 x = -0.2519943545 Simplifying x = -0.2519943545

Subproblem 2

x + 0.4444444445 = -0.19245009 Simplifying x + 0.4444444445 = -0.19245009 Reorder the terms: 0.4444444445 + x = -0.19245009 Solving 0.4444444445 + x = -0.19245009 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.4444444445' to each side of the equation. 0.4444444445 + -0.4444444445 + x = -0.19245009 + -0.4444444445 Combine like terms: 0.4444444445 + -0.4444444445 = 0.0000000000 0.0000000000 + x = -0.19245009 + -0.4444444445 x = -0.19245009 + -0.4444444445 Combine like terms: -0.19245009 + -0.4444444445 = -0.6368945345 x = -0.6368945345 Simplifying x = -0.6368945345

Solution

The solution to the problem is based on the solutions from the subproblems. x = {-0.2519943545, -0.6368945345}

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