5x^2-8x-20=0

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Solution for 5x^2-8x-20=0 equation:


Simplifying
5x2 + -8x + -20 = 0

Reorder the terms:
-20 + -8x + 5x2 = 0

Solving
-20 + -8x + 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'.
-4 + -1.6x + x2 = 0

Move the constant term to the right:

Add '4' to each side of the equation.
-4 + -1.6x + 4 + x2 = 0 + 4

Reorder the terms:
-4 + 4 + -1.6x + x2 = 0 + 4

Combine like terms: -4 + 4 = 0
0 + -1.6x + x2 = 0 + 4
-1.6x + x2 = 0 + 4

Combine like terms: 0 + 4 = 4
-1.6x + x2 = 4

The x term is -1.6x.  Take half its coefficient (-0.8).
Square it (0.64) and add it to both sides.

Add '0.64' to each side of the equation.
-1.6x + 0.64 + x2 = 4 + 0.64

Reorder the terms:
0.64 + -1.6x + x2 = 4 + 0.64

Combine like terms: 4 + 0.64 = 4.64
0.64 + -1.6x + x2 = 4.64

Factor a perfect square on the left side:
(x + -0.8)(x + -0.8) = 4.64

Calculate the square root of the right side: 2.154065923

Break this problem into two subproblems by setting 
(x + -0.8) equal to 2.154065923 and -2.154065923.

Subproblem 1

x + -0.8 = 2.154065923 Simplifying x + -0.8 = 2.154065923 Reorder the terms: -0.8 + x = 2.154065923 Solving -0.8 + x = 2.154065923 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.8' to each side of the equation. -0.8 + 0.8 + x = 2.154065923 + 0.8 Combine like terms: -0.8 + 0.8 = 0.0 0.0 + x = 2.154065923 + 0.8 x = 2.154065923 + 0.8 Combine like terms: 2.154065923 + 0.8 = 2.954065923 x = 2.954065923 Simplifying x = 2.954065923

Subproblem 2

x + -0.8 = -2.154065923 Simplifying x + -0.8 = -2.154065923 Reorder the terms: -0.8 + x = -2.154065923 Solving -0.8 + x = -2.154065923 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.8' to each side of the equation. -0.8 + 0.8 + x = -2.154065923 + 0.8 Combine like terms: -0.8 + 0.8 = 0.0 0.0 + x = -2.154065923 + 0.8 x = -2.154065923 + 0.8 Combine like terms: -2.154065923 + 0.8 = -1.354065923 x = -1.354065923 Simplifying x = -1.354065923

Solution

The solution to the problem is based on the solutions from the subproblems. x = {2.954065923, -1.354065923}

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