0=2x^2-21x-40

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Solution for 0=2x^2-21x-40 equation:


Simplifying
0 = 2x2 + -21x + -40

Reorder the terms:
0 = -40 + -21x + 2x2

Solving
0 = -40 + -21x + 2x2

Solving for variable 'x'.

Combine like terms: 0 + 40 = 40
40 + 21x + -2x2 = -40 + -21x + 2x2 + 40 + 21x + -2x2

Reorder the terms:
40 + 21x + -2x2 = -40 + 40 + -21x + 21x + 2x2 + -2x2

Combine like terms: -40 + 40 = 0
40 + 21x + -2x2 = 0 + -21x + 21x + 2x2 + -2x2
40 + 21x + -2x2 = -21x + 21x + 2x2 + -2x2

Combine like terms: -21x + 21x = 0
40 + 21x + -2x2 = 0 + 2x2 + -2x2
40 + 21x + -2x2 = 2x2 + -2x2

Combine like terms: 2x2 + -2x2 = 0
40 + 21x + -2x2 = 0

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

Divide each side by '-2'.
-20 + -10.5x + x2 = 0

Move the constant term to the right:

Add '20' to each side of the equation.
-20 + -10.5x + 20 + x2 = 0 + 20

Reorder the terms:
-20 + 20 + -10.5x + x2 = 0 + 20

Combine like terms: -20 + 20 = 0
0 + -10.5x + x2 = 0 + 20
-10.5x + x2 = 0 + 20

Combine like terms: 0 + 20 = 20
-10.5x + x2 = 20

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 = 20 + 27.5625

Reorder the terms:
27.5625 + -10.5x + x2 = 20 + 27.5625

Combine like terms: 20 + 27.5625 = 47.5625
27.5625 + -10.5x + x2 = 47.5625

Factor a perfect square on the left side:
(x + -5.25)(x + -5.25) = 47.5625

Calculate the square root of the right side: 6.896557112

Break this problem into two subproblems by setting 
(x + -5.25) equal to 6.896557112 and -6.896557112.

Subproblem 1

x + -5.25 = 6.896557112 Simplifying x + -5.25 = 6.896557112 Reorder the terms: -5.25 + x = 6.896557112 Solving -5.25 + x = 6.896557112 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 = 6.896557112 + 5.25 Combine like terms: -5.25 + 5.25 = 0.00 0.00 + x = 6.896557112 + 5.25 x = 6.896557112 + 5.25 Combine like terms: 6.896557112 + 5.25 = 12.146557112 x = 12.146557112 Simplifying x = 12.146557112

Subproblem 2

x + -5.25 = -6.896557112 Simplifying x + -5.25 = -6.896557112 Reorder the terms: -5.25 + x = -6.896557112 Solving -5.25 + x = -6.896557112 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 = -6.896557112 + 5.25 Combine like terms: -5.25 + 5.25 = 0.00 0.00 + x = -6.896557112 + 5.25 x = -6.896557112 + 5.25 Combine like terms: -6.896557112 + 5.25 = -1.646557112 x = -1.646557112 Simplifying x = -1.646557112

Solution

The solution to the problem is based on the solutions from the subproblems. x = {12.146557112, -1.646557112}

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