4x^2-x-84=0

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Solution for 4x^2-x-84=0 equation:


Simplifying
4x2 + -1x + -84 = 0

Reorder the terms:
-84 + -1x + 4x2 = 0

Solving
-84 + -1x + 4x2 = 0

Solving for variable 'x'.

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

Divide each side by '4'.
-21 + -0.25x + x2 = 0

Move the constant term to the right:

Add '21' to each side of the equation.
-21 + -0.25x + 21 + x2 = 0 + 21

Reorder the terms:
-21 + 21 + -0.25x + x2 = 0 + 21

Combine like terms: -21 + 21 = 0
0 + -0.25x + x2 = 0 + 21
-0.25x + x2 = 0 + 21

Combine like terms: 0 + 21 = 21
-0.25x + x2 = 21

The x term is -0.25x.  Take half its coefficient (-0.125).
Square it (0.015625) and add it to both sides.

Add '0.015625' to each side of the equation.
-0.25x + 0.015625 + x2 = 21 + 0.015625

Reorder the terms:
0.015625 + -0.25x + x2 = 21 + 0.015625

Combine like terms: 21 + 0.015625 = 21.015625
0.015625 + -0.25x + x2 = 21.015625

Factor a perfect square on the left side:
(x + -0.125)(x + -0.125) = 21.015625

Calculate the square root of the right side: 4.584280205

Break this problem into two subproblems by setting 
(x + -0.125) equal to 4.584280205 and -4.584280205.

Subproblem 1

x + -0.125 = 4.584280205 Simplifying x + -0.125 = 4.584280205 Reorder the terms: -0.125 + x = 4.584280205 Solving -0.125 + x = 4.584280205 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.125' to each side of the equation. -0.125 + 0.125 + x = 4.584280205 + 0.125 Combine like terms: -0.125 + 0.125 = 0.000 0.000 + x = 4.584280205 + 0.125 x = 4.584280205 + 0.125 Combine like terms: 4.584280205 + 0.125 = 4.709280205 x = 4.709280205 Simplifying x = 4.709280205

Subproblem 2

x + -0.125 = -4.584280205 Simplifying x + -0.125 = -4.584280205 Reorder the terms: -0.125 + x = -4.584280205 Solving -0.125 + x = -4.584280205 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.125' to each side of the equation. -0.125 + 0.125 + x = -4.584280205 + 0.125 Combine like terms: -0.125 + 0.125 = 0.000 0.000 + x = -4.584280205 + 0.125 x = -4.584280205 + 0.125 Combine like terms: -4.584280205 + 0.125 = -4.459280205 x = -4.459280205 Simplifying x = -4.459280205

Solution

The solution to the problem is based on the solutions from the subproblems. x = {4.709280205, -4.459280205}

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