8x^2-x-4=0

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


Simplifying
8x2 + -1x + -4 = 0

Reorder the terms:
-4 + -1x + 8x2 = 0

Solving
-4 + -1x + 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'.
-0.5 + -0.125x + x2 = 0

Move the constant term to the right:

Add '0.5' to each side of the equation.
-0.5 + -0.125x + 0.5 + x2 = 0 + 0.5

Reorder the terms:
-0.5 + 0.5 + -0.125x + x2 = 0 + 0.5

Combine like terms: -0.5 + 0.5 = 0.0
0.0 + -0.125x + x2 = 0 + 0.5
-0.125x + x2 = 0 + 0.5

Combine like terms: 0 + 0.5 = 0.5
-0.125x + x2 = 0.5

The x term is -0.125x.  Take half its coefficient (-0.0625).
Square it (0.00390625) and add it to both sides.

Add '0.00390625' to each side of the equation.
-0.125x + 0.00390625 + x2 = 0.5 + 0.00390625

Reorder the terms:
0.00390625 + -0.125x + x2 = 0.5 + 0.00390625

Combine like terms: 0.5 + 0.00390625 = 0.50390625
0.00390625 + -0.125x + x2 = 0.50390625

Factor a perfect square on the left side:
(x + -0.0625)(x + -0.0625) = 0.50390625

Calculate the square root of the right side: 0.709863543

Break this problem into two subproblems by setting 
(x + -0.0625) equal to 0.709863543 and -0.709863543.

Subproblem 1

x + -0.0625 = 0.709863543 Simplifying x + -0.0625 = 0.709863543 Reorder the terms: -0.0625 + x = 0.709863543 Solving -0.0625 + x = 0.709863543 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.0625' to each side of the equation. -0.0625 + 0.0625 + x = 0.709863543 + 0.0625 Combine like terms: -0.0625 + 0.0625 = 0.0000 0.0000 + x = 0.709863543 + 0.0625 x = 0.709863543 + 0.0625 Combine like terms: 0.709863543 + 0.0625 = 0.772363543 x = 0.772363543 Simplifying x = 0.772363543

Subproblem 2

x + -0.0625 = -0.709863543 Simplifying x + -0.0625 = -0.709863543 Reorder the terms: -0.0625 + x = -0.709863543 Solving -0.0625 + x = -0.709863543 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.0625' to each side of the equation. -0.0625 + 0.0625 + x = -0.709863543 + 0.0625 Combine like terms: -0.0625 + 0.0625 = 0.0000 0.0000 + x = -0.709863543 + 0.0625 x = -0.709863543 + 0.0625 Combine like terms: -0.709863543 + 0.0625 = -0.647363543 x = -0.647363543 Simplifying x = -0.647363543

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.772363543, -0.647363543}

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