8x^2+4x-85=0

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Solution for 8x^2+4x-85=0 equation:


Simplifying
8x2 + 4x + -85 = 0

Reorder the terms:
-85 + 4x + 8x2 = 0

Solving
-85 + 4x + 8x2 = 0

Solving for variable 'x'.

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

Divide each side by '8'.
-10.625 + 0.5x + x2 = 0

Move the constant term to the right:

Add '10.625' to each side of the equation.
-10.625 + 0.5x + 10.625 + x2 = 0 + 10.625

Reorder the terms:
-10.625 + 10.625 + 0.5x + x2 = 0 + 10.625

Combine like terms: -10.625 + 10.625 = 0.000
0.000 + 0.5x + x2 = 0 + 10.625
0.5x + x2 = 0 + 10.625

Combine like terms: 0 + 10.625 = 10.625
0.5x + x2 = 10.625

The x term is 0.5x.  Take half its coefficient (0.25).
Square it (0.0625) and add it to both sides.

Add '0.0625' to each side of the equation.
0.5x + 0.0625 + x2 = 10.625 + 0.0625

Reorder the terms:
0.0625 + 0.5x + x2 = 10.625 + 0.0625

Combine like terms: 10.625 + 0.0625 = 10.6875
0.0625 + 0.5x + x2 = 10.6875

Factor a perfect square on the left side:
(x + 0.25)(x + 0.25) = 10.6875

Calculate the square root of the right side: 3.269174208

Break this problem into two subproblems by setting 
(x + 0.25) equal to 3.269174208 and -3.269174208.

Subproblem 1

x + 0.25 = 3.269174208 Simplifying x + 0.25 = 3.269174208 Reorder the terms: 0.25 + x = 3.269174208 Solving 0.25 + x = 3.269174208 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.25' to each side of the equation. 0.25 + -0.25 + x = 3.269174208 + -0.25 Combine like terms: 0.25 + -0.25 = 0.00 0.00 + x = 3.269174208 + -0.25 x = 3.269174208 + -0.25 Combine like terms: 3.269174208 + -0.25 = 3.019174208 x = 3.019174208 Simplifying x = 3.019174208

Subproblem 2

x + 0.25 = -3.269174208 Simplifying x + 0.25 = -3.269174208 Reorder the terms: 0.25 + x = -3.269174208 Solving 0.25 + x = -3.269174208 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.25' to each side of the equation. 0.25 + -0.25 + x = -3.269174208 + -0.25 Combine like terms: 0.25 + -0.25 = 0.00 0.00 + x = -3.269174208 + -0.25 x = -3.269174208 + -0.25 Combine like terms: -3.269174208 + -0.25 = -3.519174208 x = -3.519174208 Simplifying x = -3.519174208

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.019174208, -3.519174208}

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