5x^2-8x-7=0

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Solution for 5x^2-8x-7=0 equation:


Simplifying
5x2 + -8x + -7 = 0

Reorder the terms:
-7 + -8x + 5x2 = 0

Solving
-7 + -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'.
-1.4 + -1.6x + x2 = 0

Move the constant term to the right:

Add '1.4' to each side of the equation.
-1.4 + -1.6x + 1.4 + x2 = 0 + 1.4

Reorder the terms:
-1.4 + 1.4 + -1.6x + x2 = 0 + 1.4

Combine like terms: -1.4 + 1.4 = 0.0
0.0 + -1.6x + x2 = 0 + 1.4
-1.6x + x2 = 0 + 1.4

Combine like terms: 0 + 1.4 = 1.4
-1.6x + x2 = 1.4

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 = 1.4 + 0.64

Reorder the terms:
0.64 + -1.6x + x2 = 1.4 + 0.64

Combine like terms: 1.4 + 0.64 = 2.04
0.64 + -1.6x + x2 = 2.04

Factor a perfect square on the left side:
(x + -0.8)(x + -0.8) = 2.04

Calculate the square root of the right side: 1.428285686

Break this problem into two subproblems by setting 
(x + -0.8) equal to 1.428285686 and -1.428285686.

Subproblem 1

x + -0.8 = 1.428285686 Simplifying x + -0.8 = 1.428285686 Reorder the terms: -0.8 + x = 1.428285686 Solving -0.8 + x = 1.428285686 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 = 1.428285686 + 0.8 Combine like terms: -0.8 + 0.8 = 0.0 0.0 + x = 1.428285686 + 0.8 x = 1.428285686 + 0.8 Combine like terms: 1.428285686 + 0.8 = 2.228285686 x = 2.228285686 Simplifying x = 2.228285686

Subproblem 2

x + -0.8 = -1.428285686 Simplifying x + -0.8 = -1.428285686 Reorder the terms: -0.8 + x = -1.428285686 Solving -0.8 + x = -1.428285686 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 = -1.428285686 + 0.8 Combine like terms: -0.8 + 0.8 = 0.0 0.0 + x = -1.428285686 + 0.8 x = -1.428285686 + 0.8 Combine like terms: -1.428285686 + 0.8 = -0.628285686 x = -0.628285686 Simplifying x = -0.628285686

Solution

The solution to the problem is based on the solutions from the subproblems. x = {2.228285686, -0.628285686}

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