8x^2+5x-4=0

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Solution for 8x^2+5x-4=0 equation:


Simplifying
8x2 + 5x + -4 = 0

Reorder the terms:
-4 + 5x + 8x2 = 0

Solving
-4 + 5x + 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 + 0.625x + x2 = 0

Move the constant term to the right:

Add '0.5' to each side of the equation.
-0.5 + 0.625x + 0.5 + x2 = 0 + 0.5

Reorder the terms:
-0.5 + 0.5 + 0.625x + x2 = 0 + 0.5

Combine like terms: -0.5 + 0.5 = 0.0
0.0 + 0.625x + x2 = 0 + 0.5
0.625x + x2 = 0 + 0.5

Combine like terms: 0 + 0.5 = 0.5
0.625x + x2 = 0.5

The x term is 0.625x.  Take half its coefficient (0.3125).
Square it (0.09765625) and add it to both sides.

Add '0.09765625' to each side of the equation.
0.625x + 0.09765625 + x2 = 0.5 + 0.09765625

Reorder the terms:
0.09765625 + 0.625x + x2 = 0.5 + 0.09765625

Combine like terms: 0.5 + 0.09765625 = 0.59765625
0.09765625 + 0.625x + x2 = 0.59765625

Factor a perfect square on the left side:
(x + 0.3125)(x + 0.3125) = 0.59765625

Calculate the square root of the right side: 0.773082305

Break this problem into two subproblems by setting 
(x + 0.3125) equal to 0.773082305 and -0.773082305.

Subproblem 1

x + 0.3125 = 0.773082305 Simplifying x + 0.3125 = 0.773082305 Reorder the terms: 0.3125 + x = 0.773082305 Solving 0.3125 + x = 0.773082305 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.3125' to each side of the equation. 0.3125 + -0.3125 + x = 0.773082305 + -0.3125 Combine like terms: 0.3125 + -0.3125 = 0.0000 0.0000 + x = 0.773082305 + -0.3125 x = 0.773082305 + -0.3125 Combine like terms: 0.773082305 + -0.3125 = 0.460582305 x = 0.460582305 Simplifying x = 0.460582305

Subproblem 2

x + 0.3125 = -0.773082305 Simplifying x + 0.3125 = -0.773082305 Reorder the terms: 0.3125 + x = -0.773082305 Solving 0.3125 + x = -0.773082305 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.3125' to each side of the equation. 0.3125 + -0.3125 + x = -0.773082305 + -0.3125 Combine like terms: 0.3125 + -0.3125 = 0.0000 0.0000 + x = -0.773082305 + -0.3125 x = -0.773082305 + -0.3125 Combine like terms: -0.773082305 + -0.3125 = -1.085582305 x = -1.085582305 Simplifying x = -1.085582305

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.460582305, -1.085582305}

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