2x^2-21x-28=0

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Solution for 2x^2-21x-28=0 equation:


Simplifying
2x2 + -21x + -28 = 0

Reorder the terms:
-28 + -21x + 2x2 = 0

Solving
-28 + -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'.
-14 + -10.5x + x2 = 0

Move the constant term to the right:

Add '14' to each side of the equation.
-14 + -10.5x + 14 + x2 = 0 + 14

Reorder the terms:
-14 + 14 + -10.5x + x2 = 0 + 14

Combine like terms: -14 + 14 = 0
0 + -10.5x + x2 = 0 + 14
-10.5x + x2 = 0 + 14

Combine like terms: 0 + 14 = 14
-10.5x + x2 = 14

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 = 14 + 27.5625

Reorder the terms:
27.5625 + -10.5x + x2 = 14 + 27.5625

Combine like terms: 14 + 27.5625 = 41.5625
27.5625 + -10.5x + x2 = 41.5625

Factor a perfect square on the left side:
(x + -5.25)(x + -5.25) = 41.5625

Calculate the square root of the right side: 6.446898479

Break this problem into two subproblems by setting 
(x + -5.25) equal to 6.446898479 and -6.446898479.

Subproblem 1

x + -5.25 = 6.446898479 Simplifying x + -5.25 = 6.446898479 Reorder the terms: -5.25 + x = 6.446898479 Solving -5.25 + x = 6.446898479 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 = 6.446898479 + 5.25 Combine like terms: -5.25 + 5.25 = 0.00 0.00 + x = 6.446898479 + 5.25 x = 6.446898479 + 5.25 Combine like terms: 6.446898479 + 5.25 = 11.696898479 x = 11.696898479 Simplifying x = 11.696898479

Subproblem 2

x + -5.25 = -6.446898479 Simplifying x + -5.25 = -6.446898479 Reorder the terms: -5.25 + x = -6.446898479 Solving -5.25 + x = -6.446898479 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 = -6.446898479 + 5.25 Combine like terms: -5.25 + 5.25 = 0.00 0.00 + x = -6.446898479 + 5.25 x = -6.446898479 + 5.25 Combine like terms: -6.446898479 + 5.25 = -1.196898479 x = -1.196898479 Simplifying x = -1.196898479

Solution

The solution to the problem is based on the solutions from the subproblems. x = {11.696898479, -1.196898479}

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