5x^2+x-8=0

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


Simplifying
5x2 + x + -8 = 0

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

Solving
-8 + x + 5x2 = 0

Solving for variable 'x'.

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

Divide each side by '5'.
-1.6 + 0.2x + x2 = 0

Move the constant term to the right:

Add '1.6' to each side of the equation.
-1.6 + 0.2x + 1.6 + x2 = 0 + 1.6

Reorder the terms:
-1.6 + 1.6 + 0.2x + x2 = 0 + 1.6

Combine like terms: -1.6 + 1.6 = 0.0
0.0 + 0.2x + x2 = 0 + 1.6
0.2x + x2 = 0 + 1.6

Combine like terms: 0 + 1.6 = 1.6
0.2x + x2 = 1.6

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

Add '0.25' to each side of the equation.
0.2x + 0.25 + x2 = 1.6 + 0.25

Reorder the terms:
0.25 + 0.2x + x2 = 1.6 + 0.25

Combine like terms: 1.6 + 0.25 = 1.85
0.25 + 0.2x + x2 = 1.85

Factor a perfect square on the left side:
(x + 0.5)(x + 0.5) = 1.85

Calculate the square root of the right side: 1.360147051

Break this problem into two subproblems by setting 
(x + 0.5) equal to 1.360147051 and -1.360147051.

Subproblem 1

x + 0.5 = 1.360147051 Simplifying x + 0.5 = 1.360147051 Reorder the terms: 0.5 + x = 1.360147051 Solving 0.5 + x = 1.360147051 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.5' to each side of the equation. 0.5 + -0.5 + x = 1.360147051 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + x = 1.360147051 + -0.5 x = 1.360147051 + -0.5 Combine like terms: 1.360147051 + -0.5 = 0.860147051 x = 0.860147051 Simplifying x = 0.860147051

Subproblem 2

x + 0.5 = -1.360147051 Simplifying x + 0.5 = -1.360147051 Reorder the terms: 0.5 + x = -1.360147051 Solving 0.5 + x = -1.360147051 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.5' to each side of the equation. 0.5 + -0.5 + x = -1.360147051 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + x = -1.360147051 + -0.5 x = -1.360147051 + -0.5 Combine like terms: -1.360147051 + -0.5 = -1.860147051 x = -1.860147051 Simplifying x = -1.860147051

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.860147051, -1.860147051}

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