2x^2-3x-84=0

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Solution for 2x^2-3x-84=0 equation:


Simplifying
2x2 + -3x + -84 = 0

Reorder the terms:
-84 + -3x + 2x2 = 0

Solving
-84 + -3x + 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 + -1.5x + x2 = 0

Move the constant term to the right:

Add '42' to each side of the equation.
-42 + -1.5x + 42 + x2 = 0 + 42

Reorder the terms:
-42 + 42 + -1.5x + x2 = 0 + 42

Combine like terms: -42 + 42 = 0
0 + -1.5x + x2 = 0 + 42
-1.5x + x2 = 0 + 42

Combine like terms: 0 + 42 = 42
-1.5x + x2 = 42

The x term is -1.5x.  Take half its coefficient (-0.75).
Square it (0.5625) and add it to both sides.

Add '0.5625' to each side of the equation.
-1.5x + 0.5625 + x2 = 42 + 0.5625

Reorder the terms:
0.5625 + -1.5x + x2 = 42 + 0.5625

Combine like terms: 42 + 0.5625 = 42.5625
0.5625 + -1.5x + x2 = 42.5625

Factor a perfect square on the left side:
(x + -0.75)(x + -0.75) = 42.5625

Calculate the square root of the right side: 6.523994175

Break this problem into two subproblems by setting 
(x + -0.75) equal to 6.523994175 and -6.523994175.

Subproblem 1

x + -0.75 = 6.523994175 Simplifying x + -0.75 = 6.523994175 Reorder the terms: -0.75 + x = 6.523994175 Solving -0.75 + x = 6.523994175 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.75' to each side of the equation. -0.75 + 0.75 + x = 6.523994175 + 0.75 Combine like terms: -0.75 + 0.75 = 0.00 0.00 + x = 6.523994175 + 0.75 x = 6.523994175 + 0.75 Combine like terms: 6.523994175 + 0.75 = 7.273994175 x = 7.273994175 Simplifying x = 7.273994175

Subproblem 2

x + -0.75 = -6.523994175 Simplifying x + -0.75 = -6.523994175 Reorder the terms: -0.75 + x = -6.523994175 Solving -0.75 + x = -6.523994175 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.75' to each side of the equation. -0.75 + 0.75 + x = -6.523994175 + 0.75 Combine like terms: -0.75 + 0.75 = 0.00 0.00 + x = -6.523994175 + 0.75 x = -6.523994175 + 0.75 Combine like terms: -6.523994175 + 0.75 = -5.773994175 x = -5.773994175 Simplifying x = -5.773994175

Solution

The solution to the problem is based on the solutions from the subproblems. x = {7.273994175, -5.773994175}

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