5x^2-x-4=8

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


Simplifying
5x2 + -1x + -4 = 8

Reorder the terms:
-4 + -1x + 5x2 = 8

Solving
-4 + -1x + 5x2 = 8

Solving for variable 'x'.

Reorder the terms:
-4 + -8 + -1x + 5x2 = 8 + -8

Combine like terms: -4 + -8 = -12
-12 + -1x + 5x2 = 8 + -8

Combine like terms: 8 + -8 = 0
-12 + -1x + 5x2 = 0

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

Divide each side by '5'.
-2.4 + -0.2x + x2 = 0

Move the constant term to the right:

Add '2.4' to each side of the equation.
-2.4 + -0.2x + 2.4 + x2 = 0 + 2.4

Reorder the terms:
-2.4 + 2.4 + -0.2x + x2 = 0 + 2.4

Combine like terms: -2.4 + 2.4 = 0.0
0.0 + -0.2x + x2 = 0 + 2.4
-0.2x + x2 = 0 + 2.4

Combine like terms: 0 + 2.4 = 2.4
-0.2x + x2 = 2.4

The x term is -0.2x.  Take half its coefficient (-0.1).
Square it (0.01) and add it to both sides.

Add '0.01' to each side of the equation.
-0.2x + 0.01 + x2 = 2.4 + 0.01

Reorder the terms:
0.01 + -0.2x + x2 = 2.4 + 0.01

Combine like terms: 2.4 + 0.01 = 2.41
0.01 + -0.2x + x2 = 2.41

Factor a perfect square on the left side:
(x + -0.1)(x + -0.1) = 2.41

Calculate the square root of the right side: 1.55241747

Break this problem into two subproblems by setting 
(x + -0.1) equal to 1.55241747 and -1.55241747.

Subproblem 1

x + -0.1 = 1.55241747 Simplifying x + -0.1 = 1.55241747 Reorder the terms: -0.1 + x = 1.55241747 Solving -0.1 + x = 1.55241747 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.1' to each side of the equation. -0.1 + 0.1 + x = 1.55241747 + 0.1 Combine like terms: -0.1 + 0.1 = 0.0 0.0 + x = 1.55241747 + 0.1 x = 1.55241747 + 0.1 Combine like terms: 1.55241747 + 0.1 = 1.65241747 x = 1.65241747 Simplifying x = 1.65241747

Subproblem 2

x + -0.1 = -1.55241747 Simplifying x + -0.1 = -1.55241747 Reorder the terms: -0.1 + x = -1.55241747 Solving -0.1 + x = -1.55241747 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.1' to each side of the equation. -0.1 + 0.1 + x = -1.55241747 + 0.1 Combine like terms: -0.1 + 0.1 = 0.0 0.0 + x = -1.55241747 + 0.1 x = -1.55241747 + 0.1 Combine like terms: -1.55241747 + 0.1 = -1.45241747 x = -1.45241747 Simplifying x = -1.45241747

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.65241747, -1.45241747}

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