5x^2-4x-40=0

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Solution for 5x^2-4x-40=0 equation:


Simplifying
5x2 + -4x + -40 = 0

Reorder the terms:
-40 + -4x + 5x2 = 0

Solving
-40 + -4x + 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'.
-8 + -0.8x + x2 = 0

Move the constant term to the right:

Add '8' to each side of the equation.
-8 + -0.8x + 8 + x2 = 0 + 8

Reorder the terms:
-8 + 8 + -0.8x + x2 = 0 + 8

Combine like terms: -8 + 8 = 0
0 + -0.8x + x2 = 0 + 8
-0.8x + x2 = 0 + 8

Combine like terms: 0 + 8 = 8
-0.8x + x2 = 8

The x term is -0.8x.  Take half its coefficient (-0.4).
Square it (0.16) and add it to both sides.

Add '0.16' to each side of the equation.
-0.8x + 0.16 + x2 = 8 + 0.16

Reorder the terms:
0.16 + -0.8x + x2 = 8 + 0.16

Combine like terms: 8 + 0.16 = 8.16
0.16 + -0.8x + x2 = 8.16

Factor a perfect square on the left side:
(x + -0.4)(x + -0.4) = 8.16

Calculate the square root of the right side: 2.856571371

Break this problem into two subproblems by setting 
(x + -0.4) equal to 2.856571371 and -2.856571371.

Subproblem 1

x + -0.4 = 2.856571371 Simplifying x + -0.4 = 2.856571371 Reorder the terms: -0.4 + x = 2.856571371 Solving -0.4 + x = 2.856571371 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.4' to each side of the equation. -0.4 + 0.4 + x = 2.856571371 + 0.4 Combine like terms: -0.4 + 0.4 = 0.0 0.0 + x = 2.856571371 + 0.4 x = 2.856571371 + 0.4 Combine like terms: 2.856571371 + 0.4 = 3.256571371 x = 3.256571371 Simplifying x = 3.256571371

Subproblem 2

x + -0.4 = -2.856571371 Simplifying x + -0.4 = -2.856571371 Reorder the terms: -0.4 + x = -2.856571371 Solving -0.4 + x = -2.856571371 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.4' to each side of the equation. -0.4 + 0.4 + x = -2.856571371 + 0.4 Combine like terms: -0.4 + 0.4 = 0.0 0.0 + x = -2.856571371 + 0.4 x = -2.856571371 + 0.4 Combine like terms: -2.856571371 + 0.4 = -2.456571371 x = -2.456571371 Simplifying x = -2.456571371

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.256571371, -2.456571371}

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