5x^2-28x-15=0

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Solution for 5x^2-28x-15=0 equation:


Simplifying
5x2 + -28x + -15 = 0

Reorder the terms:
-15 + -28x + 5x2 = 0

Solving
-15 + -28x + 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'.
-3 + -5.6x + x2 = 0

Move the constant term to the right:

Add '3' to each side of the equation.
-3 + -5.6x + 3 + x2 = 0 + 3

Reorder the terms:
-3 + 3 + -5.6x + x2 = 0 + 3

Combine like terms: -3 + 3 = 0
0 + -5.6x + x2 = 0 + 3
-5.6x + x2 = 0 + 3

Combine like terms: 0 + 3 = 3
-5.6x + x2 = 3

The x term is -5.6x.  Take half its coefficient (-2.8).
Square it (7.84) and add it to both sides.

Add '7.84' to each side of the equation.
-5.6x + 7.84 + x2 = 3 + 7.84

Reorder the terms:
7.84 + -5.6x + x2 = 3 + 7.84

Combine like terms: 3 + 7.84 = 10.84
7.84 + -5.6x + x2 = 10.84

Factor a perfect square on the left side:
(x + -2.8)(x + -2.8) = 10.84

Calculate the square root of the right side: 3.292415527

Break this problem into two subproblems by setting 
(x + -2.8) equal to 3.292415527 and -3.292415527.

Subproblem 1

x + -2.8 = 3.292415527 Simplifying x + -2.8 = 3.292415527 Reorder the terms: -2.8 + x = 3.292415527 Solving -2.8 + x = 3.292415527 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2.8' to each side of the equation. -2.8 + 2.8 + x = 3.292415527 + 2.8 Combine like terms: -2.8 + 2.8 = 0.0 0.0 + x = 3.292415527 + 2.8 x = 3.292415527 + 2.8 Combine like terms: 3.292415527 + 2.8 = 6.092415527 x = 6.092415527 Simplifying x = 6.092415527

Subproblem 2

x + -2.8 = -3.292415527 Simplifying x + -2.8 = -3.292415527 Reorder the terms: -2.8 + x = -3.292415527 Solving -2.8 + x = -3.292415527 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2.8' to each side of the equation. -2.8 + 2.8 + x = -3.292415527 + 2.8 Combine like terms: -2.8 + 2.8 = 0.0 0.0 + x = -3.292415527 + 2.8 x = -3.292415527 + 2.8 Combine like terms: -3.292415527 + 2.8 = -0.492415527 x = -0.492415527 Simplifying x = -0.492415527

Solution

The solution to the problem is based on the solutions from the subproblems. x = {6.092415527, -0.492415527}

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