81x^2+18x-4=0

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Solution for 81x^2+18x-4=0 equation:


Simplifying
81x2 + 18x + -4 = 0

Reorder the terms:
-4 + 18x + 81x2 = 0

Solving
-4 + 18x + 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'.
-0.04938271605 + 0.2222222222x + x2 = 0

Move the constant term to the right:

Add '0.04938271605' to each side of the equation.
-0.04938271605 + 0.2222222222x + 0.04938271605 + x2 = 0 + 0.04938271605

Reorder the terms:
-0.04938271605 + 0.04938271605 + 0.2222222222x + x2 = 0 + 0.04938271605

Combine like terms: -0.04938271605 + 0.04938271605 = 0.00000000000
0.00000000000 + 0.2222222222x + x2 = 0 + 0.04938271605
0.2222222222x + x2 = 0 + 0.04938271605

Combine like terms: 0 + 0.04938271605 = 0.04938271605
0.2222222222x + x2 = 0.04938271605

The x term is 0.2222222222x.  Take half its coefficient (0.1111111111).
Square it (0.01234567901) and add it to both sides.

Add '0.01234567901' to each side of the equation.
0.2222222222x + 0.01234567901 + x2 = 0.04938271605 + 0.01234567901

Reorder the terms:
0.01234567901 + 0.2222222222x + x2 = 0.04938271605 + 0.01234567901

Combine like terms: 0.04938271605 + 0.01234567901 = 0.06172839506
0.01234567901 + 0.2222222222x + x2 = 0.06172839506

Factor a perfect square on the left side:
(x + 0.1111111111)(x + 0.1111111111) = 0.06172839506

Calculate the square root of the right side: 0.248451997

Break this problem into two subproblems by setting 
(x + 0.1111111111) equal to 0.248451997 and -0.248451997.

Subproblem 1

x + 0.1111111111 = 0.248451997 Simplifying x + 0.1111111111 = 0.248451997 Reorder the terms: 0.1111111111 + x = 0.248451997 Solving 0.1111111111 + x = 0.248451997 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.1111111111' to each side of the equation. 0.1111111111 + -0.1111111111 + x = 0.248451997 + -0.1111111111 Combine like terms: 0.1111111111 + -0.1111111111 = 0.0000000000 0.0000000000 + x = 0.248451997 + -0.1111111111 x = 0.248451997 + -0.1111111111 Combine like terms: 0.248451997 + -0.1111111111 = 0.1373408859 x = 0.1373408859 Simplifying x = 0.1373408859

Subproblem 2

x + 0.1111111111 = -0.248451997 Simplifying x + 0.1111111111 = -0.248451997 Reorder the terms: 0.1111111111 + x = -0.248451997 Solving 0.1111111111 + x = -0.248451997 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.1111111111' to each side of the equation. 0.1111111111 + -0.1111111111 + x = -0.248451997 + -0.1111111111 Combine like terms: 0.1111111111 + -0.1111111111 = 0.0000000000 0.0000000000 + x = -0.248451997 + -0.1111111111 x = -0.248451997 + -0.1111111111 Combine like terms: -0.248451997 + -0.1111111111 = -0.3595631081 x = -0.3595631081 Simplifying x = -0.3595631081

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.1373408859, -0.3595631081}

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