21k^2+4k-4=0

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Solution for 21k^2+4k-4=0 equation:


Simplifying
21k2 + 4k + -4 = 0

Reorder the terms:
-4 + 4k + 21k2 = 0

Solving
-4 + 4k + 21k2 = 0

Solving for variable 'k'.

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

Divide each side by '21'.
-0.1904761905 + 0.1904761905k + k2 = 0

Move the constant term to the right:

Add '0.1904761905' to each side of the equation.
-0.1904761905 + 0.1904761905k + 0.1904761905 + k2 = 0 + 0.1904761905

Reorder the terms:
-0.1904761905 + 0.1904761905 + 0.1904761905k + k2 = 0 + 0.1904761905

Combine like terms: -0.1904761905 + 0.1904761905 = 0.0000000000
0.0000000000 + 0.1904761905k + k2 = 0 + 0.1904761905
0.1904761905k + k2 = 0 + 0.1904761905

Combine like terms: 0 + 0.1904761905 = 0.1904761905
0.1904761905k + k2 = 0.1904761905

The k term is 0.1904761905k.  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.
0.1904761905k + 0.009070294787 + k2 = 0.1904761905 + 0.009070294787

Reorder the terms:
0.009070294787 + 0.1904761905k + k2 = 0.1904761905 + 0.009070294787

Combine like terms: 0.1904761905 + 0.009070294787 = 0.199546485287
0.009070294787 + 0.1904761905k + k2 = 0.199546485287

Factor a perfect square on the left side:
(k + 0.09523809525)(k + 0.09523809525) = 0.199546485287

Calculate the square root of the right side: 0.446706263

Break this problem into two subproblems by setting 
(k + 0.09523809525) equal to 0.446706263 and -0.446706263.

Subproblem 1

k + 0.09523809525 = 0.446706263 Simplifying k + 0.09523809525 = 0.446706263 Reorder the terms: 0.09523809525 + k = 0.446706263 Solving 0.09523809525 + k = 0.446706263 Solving for variable 'k'. Move all terms containing k to the left, all other terms to the right. Add '-0.09523809525' to each side of the equation. 0.09523809525 + -0.09523809525 + k = 0.446706263 + -0.09523809525 Combine like terms: 0.09523809525 + -0.09523809525 = 0.00000000000 0.00000000000 + k = 0.446706263 + -0.09523809525 k = 0.446706263 + -0.09523809525 Combine like terms: 0.446706263 + -0.09523809525 = 0.35146816775 k = 0.35146816775 Simplifying k = 0.35146816775

Subproblem 2

k + 0.09523809525 = -0.446706263 Simplifying k + 0.09523809525 = -0.446706263 Reorder the terms: 0.09523809525 + k = -0.446706263 Solving 0.09523809525 + k = -0.446706263 Solving for variable 'k'. Move all terms containing k to the left, all other terms to the right. Add '-0.09523809525' to each side of the equation. 0.09523809525 + -0.09523809525 + k = -0.446706263 + -0.09523809525 Combine like terms: 0.09523809525 + -0.09523809525 = 0.00000000000 0.00000000000 + k = -0.446706263 + -0.09523809525 k = -0.446706263 + -0.09523809525 Combine like terms: -0.446706263 + -0.09523809525 = -0.54194435825 k = -0.54194435825 Simplifying k = -0.54194435825

Solution

The solution to the problem is based on the solutions from the subproblems. k = {0.35146816775, -0.54194435825}

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