2x^2-21x-108=0

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Solution for 2x^2-21x-108=0 equation:


Simplifying
2x2 + -21x + -108 = 0

Reorder the terms:
-108 + -21x + 2x2 = 0

Solving
-108 + -21x + 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'.
-54 + -10.5x + x2 = 0

Move the constant term to the right:

Add '54' to each side of the equation.
-54 + -10.5x + 54 + x2 = 0 + 54

Reorder the terms:
-54 + 54 + -10.5x + x2 = 0 + 54

Combine like terms: -54 + 54 = 0
0 + -10.5x + x2 = 0 + 54
-10.5x + x2 = 0 + 54

Combine like terms: 0 + 54 = 54
-10.5x + x2 = 54

The x term is -10.5x.  Take half its coefficient (-5.25).
Square it (27.5625) and add it to both sides.

Add '27.5625' to each side of the equation.
-10.5x + 27.5625 + x2 = 54 + 27.5625

Reorder the terms:
27.5625 + -10.5x + x2 = 54 + 27.5625

Combine like terms: 54 + 27.5625 = 81.5625
27.5625 + -10.5x + x2 = 81.5625

Factor a perfect square on the left side:
(x + -5.25)(x + -5.25) = 81.5625

Calculate the square root of the right side: 9.031195934

Break this problem into two subproblems by setting 
(x + -5.25) equal to 9.031195934 and -9.031195934.

Subproblem 1

x + -5.25 = 9.031195934 Simplifying x + -5.25 = 9.031195934 Reorder the terms: -5.25 + x = 9.031195934 Solving -5.25 + x = 9.031195934 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '5.25' to each side of the equation. -5.25 + 5.25 + x = 9.031195934 + 5.25 Combine like terms: -5.25 + 5.25 = 0.00 0.00 + x = 9.031195934 + 5.25 x = 9.031195934 + 5.25 Combine like terms: 9.031195934 + 5.25 = 14.281195934 x = 14.281195934 Simplifying x = 14.281195934

Subproblem 2

x + -5.25 = -9.031195934 Simplifying x + -5.25 = -9.031195934 Reorder the terms: -5.25 + x = -9.031195934 Solving -5.25 + x = -9.031195934 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '5.25' to each side of the equation. -5.25 + 5.25 + x = -9.031195934 + 5.25 Combine like terms: -5.25 + 5.25 = 0.00 0.00 + x = -9.031195934 + 5.25 x = -9.031195934 + 5.25 Combine like terms: -9.031195934 + 5.25 = -3.781195934 x = -3.781195934 Simplifying x = -3.781195934

Solution

The solution to the problem is based on the solutions from the subproblems. x = {14.281195934, -3.781195934}

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