2x^2-x-42=0

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Solution for 2x^2-x-42=0 equation:


Simplifying
2x2 + -1x + -42 = 0

Reorder the terms:
-42 + -1x + 2x2 = 0

Solving
-42 + -1x + 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'.
-21 + -0.5x + x2 = 0

Move the constant term to the right:

Add '21' to each side of the equation.
-21 + -0.5x + 21 + x2 = 0 + 21

Reorder the terms:
-21 + 21 + -0.5x + x2 = 0 + 21

Combine like terms: -21 + 21 = 0
0 + -0.5x + x2 = 0 + 21
-0.5x + x2 = 0 + 21

Combine like terms: 0 + 21 = 21
-0.5x + x2 = 21

The x term is -0.5x.  Take half its coefficient (-0.25).
Square it (0.0625) and add it to both sides.

Add '0.0625' to each side of the equation.
-0.5x + 0.0625 + x2 = 21 + 0.0625

Reorder the terms:
0.0625 + -0.5x + x2 = 21 + 0.0625

Combine like terms: 21 + 0.0625 = 21.0625
0.0625 + -0.5x + x2 = 21.0625

Factor a perfect square on the left side:
(x + -0.25)(x + -0.25) = 21.0625

Calculate the square root of the right side: 4.589389938

Break this problem into two subproblems by setting 
(x + -0.25) equal to 4.589389938 and -4.589389938.

Subproblem 1

x + -0.25 = 4.589389938 Simplifying x + -0.25 = 4.589389938 Reorder the terms: -0.25 + x = 4.589389938 Solving -0.25 + x = 4.589389938 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.25' to each side of the equation. -0.25 + 0.25 + x = 4.589389938 + 0.25 Combine like terms: -0.25 + 0.25 = 0.00 0.00 + x = 4.589389938 + 0.25 x = 4.589389938 + 0.25 Combine like terms: 4.589389938 + 0.25 = 4.839389938 x = 4.839389938 Simplifying x = 4.839389938

Subproblem 2

x + -0.25 = -4.589389938 Simplifying x + -0.25 = -4.589389938 Reorder the terms: -0.25 + x = -4.589389938 Solving -0.25 + x = -4.589389938 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.25' to each side of the equation. -0.25 + 0.25 + x = -4.589389938 + 0.25 Combine like terms: -0.25 + 0.25 = 0.00 0.00 + x = -4.589389938 + 0.25 x = -4.589389938 + 0.25 Combine like terms: -4.589389938 + 0.25 = -4.339389938 x = -4.339389938 Simplifying x = -4.339389938

Solution

The solution to the problem is based on the solutions from the subproblems. x = {4.839389938, -4.339389938}

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