8x^2-4x-9=0

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Solution for 8x^2-4x-9=0 equation:


Simplifying
8x2 + -4x + -9 = 0

Reorder the terms:
-9 + -4x + 8x2 = 0

Solving
-9 + -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'.
-1.125 + -0.5x + x2 = 0

Move the constant term to the right:

Add '1.125' to each side of the equation.
-1.125 + -0.5x + 1.125 + x2 = 0 + 1.125

Reorder the terms:
-1.125 + 1.125 + -0.5x + x2 = 0 + 1.125

Combine like terms: -1.125 + 1.125 = 0.000
0.000 + -0.5x + x2 = 0 + 1.125
-0.5x + x2 = 0 + 1.125

Combine like terms: 0 + 1.125 = 1.125
-0.5x + x2 = 1.125

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 = 1.125 + 0.0625

Reorder the terms:
0.0625 + -0.5x + x2 = 1.125 + 0.0625

Combine like terms: 1.125 + 0.0625 = 1.1875
0.0625 + -0.5x + x2 = 1.1875

Factor a perfect square on the left side:
(x + -0.25)(x + -0.25) = 1.1875

Calculate the square root of the right side: 1.089724736

Break this problem into two subproblems by setting 
(x + -0.25) equal to 1.089724736 and -1.089724736.

Subproblem 1

x + -0.25 = 1.089724736 Simplifying x + -0.25 = 1.089724736 Reorder the terms: -0.25 + x = 1.089724736 Solving -0.25 + x = 1.089724736 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 = 1.089724736 + 0.25 Combine like terms: -0.25 + 0.25 = 0.00 0.00 + x = 1.089724736 + 0.25 x = 1.089724736 + 0.25 Combine like terms: 1.089724736 + 0.25 = 1.339724736 x = 1.339724736 Simplifying x = 1.339724736

Subproblem 2

x + -0.25 = -1.089724736 Simplifying x + -0.25 = -1.089724736 Reorder the terms: -0.25 + x = -1.089724736 Solving -0.25 + x = -1.089724736 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 = -1.089724736 + 0.25 Combine like terms: -0.25 + 0.25 = 0.00 0.00 + x = -1.089724736 + 0.25 x = -1.089724736 + 0.25 Combine like terms: -1.089724736 + 0.25 = -0.839724736 x = -0.839724736 Simplifying x = -0.839724736

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.339724736, -0.839724736}

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