21x^2-4x-40=0

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Solution for 21x^2-4x-40=0 equation:


Simplifying
21x2 + -4x + -40 = 0

Reorder the terms:
-40 + -4x + 21x2 = 0

Solving
-40 + -4x + 21x2 = 0

Solving for variable 'x'.

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

Divide each side by '21'.
-1.904761905 + -0.1904761905x + x2 = 0

Move the constant term to the right:

Add '1.904761905' to each side of the equation.
-1.904761905 + -0.1904761905x + 1.904761905 + x2 = 0 + 1.904761905

Reorder the terms:
-1.904761905 + 1.904761905 + -0.1904761905x + x2 = 0 + 1.904761905

Combine like terms: -1.904761905 + 1.904761905 = 0.000000000
0.000000000 + -0.1904761905x + x2 = 0 + 1.904761905
-0.1904761905x + x2 = 0 + 1.904761905

Combine like terms: 0 + 1.904761905 = 1.904761905
-0.1904761905x + x2 = 1.904761905

The x term is -0.1904761905x.  Take half its coefficient (-0.09523809525).
Square it (0.009070294787) and add it to both sides.

Add '0.009070294787' to each side of the equation.
-0.1904761905x + 0.009070294787 + x2 = 1.904761905 + 0.009070294787

Reorder the terms:
0.009070294787 + -0.1904761905x + x2 = 1.904761905 + 0.009070294787

Combine like terms: 1.904761905 + 0.009070294787 = 1.913832199787
0.009070294787 + -0.1904761905x + x2 = 1.913832199787

Factor a perfect square on the left side:
(x + -0.09523809525)(x + -0.09523809525) = 1.913832199787

Calculate the square root of the right side: 1.383413243

Break this problem into two subproblems by setting 
(x + -0.09523809525) equal to 1.383413243 and -1.383413243.

Subproblem 1

x + -0.09523809525 = 1.383413243 Simplifying x + -0.09523809525 = 1.383413243 Reorder the terms: -0.09523809525 + x = 1.383413243 Solving -0.09523809525 + x = 1.383413243 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.09523809525' to each side of the equation. -0.09523809525 + 0.09523809525 + x = 1.383413243 + 0.09523809525 Combine like terms: -0.09523809525 + 0.09523809525 = 0.00000000000 0.00000000000 + x = 1.383413243 + 0.09523809525 x = 1.383413243 + 0.09523809525 Combine like terms: 1.383413243 + 0.09523809525 = 1.47865133825 x = 1.47865133825 Simplifying x = 1.47865133825

Subproblem 2

x + -0.09523809525 = -1.383413243 Simplifying x + -0.09523809525 = -1.383413243 Reorder the terms: -0.09523809525 + x = -1.383413243 Solving -0.09523809525 + x = -1.383413243 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.09523809525' to each side of the equation. -0.09523809525 + 0.09523809525 + x = -1.383413243 + 0.09523809525 Combine like terms: -0.09523809525 + 0.09523809525 = 0.00000000000 0.00000000000 + x = -1.383413243 + 0.09523809525 x = -1.383413243 + 0.09523809525 Combine like terms: -1.383413243 + 0.09523809525 = -1.28817514775 x = -1.28817514775 Simplifying x = -1.28817514775

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.47865133825, -1.28817514775}

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