2x^2-15x-84=0

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Solution for 2x^2-15x-84=0 equation:


Simplifying
2x2 + -15x + -84 = 0

Reorder the terms:
-84 + -15x + 2x2 = 0

Solving
-84 + -15x + 2x2 = 0

Solving for variable 'x'.

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

Divide each side by '2'.
-42 + -7.5x + x2 = 0

Move the constant term to the right:

Add '42' to each side of the equation.
-42 + -7.5x + 42 + x2 = 0 + 42

Reorder the terms:
-42 + 42 + -7.5x + x2 = 0 + 42

Combine like terms: -42 + 42 = 0
0 + -7.5x + x2 = 0 + 42
-7.5x + x2 = 0 + 42

Combine like terms: 0 + 42 = 42
-7.5x + x2 = 42

The x term is -7.5x.  Take half its coefficient (-3.75).
Square it (14.0625) and add it to both sides.

Add '14.0625' to each side of the equation.
-7.5x + 14.0625 + x2 = 42 + 14.0625

Reorder the terms:
14.0625 + -7.5x + x2 = 42 + 14.0625

Combine like terms: 42 + 14.0625 = 56.0625
14.0625 + -7.5x + x2 = 56.0625

Factor a perfect square on the left side:
(x + -3.75)(x + -3.75) = 56.0625

Calculate the square root of the right side: 7.487489566

Break this problem into two subproblems by setting 
(x + -3.75) equal to 7.487489566 and -7.487489566.

Subproblem 1

x + -3.75 = 7.487489566 Simplifying x + -3.75 = 7.487489566 Reorder the terms: -3.75 + x = 7.487489566 Solving -3.75 + x = 7.487489566 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '3.75' to each side of the equation. -3.75 + 3.75 + x = 7.487489566 + 3.75 Combine like terms: -3.75 + 3.75 = 0.00 0.00 + x = 7.487489566 + 3.75 x = 7.487489566 + 3.75 Combine like terms: 7.487489566 + 3.75 = 11.237489566 x = 11.237489566 Simplifying x = 11.237489566

Subproblem 2

x + -3.75 = -7.487489566 Simplifying x + -3.75 = -7.487489566 Reorder the terms: -3.75 + x = -7.487489566 Solving -3.75 + x = -7.487489566 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '3.75' to each side of the equation. -3.75 + 3.75 + x = -7.487489566 + 3.75 Combine like terms: -3.75 + 3.75 = 0.00 0.00 + x = -7.487489566 + 3.75 x = -7.487489566 + 3.75 Combine like terms: -7.487489566 + 3.75 = -3.737489566 x = -3.737489566 Simplifying x = -3.737489566

Solution

The solution to the problem is based on the solutions from the subproblems. x = {11.237489566, -3.737489566}

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