10c^2-6c-21=0

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Solution for 10c^2-6c-21=0 equation:


Simplifying
10c2 + -6c + -21 = 0

Reorder the terms:
-21 + -6c + 10c2 = 0

Solving
-21 + -6c + 10c2 = 0

Solving for variable 'c'.

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

Divide each side by '10'.
-2.1 + -0.6c + c2 = 0

Move the constant term to the right:

Add '2.1' to each side of the equation.
-2.1 + -0.6c + 2.1 + c2 = 0 + 2.1

Reorder the terms:
-2.1 + 2.1 + -0.6c + c2 = 0 + 2.1

Combine like terms: -2.1 + 2.1 = 0.0
0.0 + -0.6c + c2 = 0 + 2.1
-0.6c + c2 = 0 + 2.1

Combine like terms: 0 + 2.1 = 2.1
-0.6c + c2 = 2.1

The c term is -0.6c.  Take half its coefficient (-0.3).
Square it (0.09) and add it to both sides.

Add '0.09' to each side of the equation.
-0.6c + 0.09 + c2 = 2.1 + 0.09

Reorder the terms:
0.09 + -0.6c + c2 = 2.1 + 0.09

Combine like terms: 2.1 + 0.09 = 2.19
0.09 + -0.6c + c2 = 2.19

Factor a perfect square on the left side:
(c + -0.3)(c + -0.3) = 2.19

Calculate the square root of the right side: 1.479864859

Break this problem into two subproblems by setting 
(c + -0.3) equal to 1.479864859 and -1.479864859.

Subproblem 1

c + -0.3 = 1.479864859 Simplifying c + -0.3 = 1.479864859 Reorder the terms: -0.3 + c = 1.479864859 Solving -0.3 + c = 1.479864859 Solving for variable 'c'. Move all terms containing c to the left, all other terms to the right. Add '0.3' to each side of the equation. -0.3 + 0.3 + c = 1.479864859 + 0.3 Combine like terms: -0.3 + 0.3 = 0.0 0.0 + c = 1.479864859 + 0.3 c = 1.479864859 + 0.3 Combine like terms: 1.479864859 + 0.3 = 1.779864859 c = 1.779864859 Simplifying c = 1.779864859

Subproblem 2

c + -0.3 = -1.479864859 Simplifying c + -0.3 = -1.479864859 Reorder the terms: -0.3 + c = -1.479864859 Solving -0.3 + c = -1.479864859 Solving for variable 'c'. Move all terms containing c to the left, all other terms to the right. Add '0.3' to each side of the equation. -0.3 + 0.3 + c = -1.479864859 + 0.3 Combine like terms: -0.3 + 0.3 = 0.0 0.0 + c = -1.479864859 + 0.3 c = -1.479864859 + 0.3 Combine like terms: -1.479864859 + 0.3 = -1.179864859 c = -1.179864859 Simplifying c = -1.179864859

Solution

The solution to the problem is based on the solutions from the subproblems. c = {1.779864859, -1.179864859}

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