c^2-18c-80=0

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Solution for c^2-18c-80=0 equation:


Simplifying
c2 + -18c + -80 = 0

Reorder the terms:
-80 + -18c + c2 = 0

Solving
-80 + -18c + c2 = 0

Solving for variable 'c'.

Begin completing the square.

Move the constant term to the right:

Add '80' to each side of the equation.
-80 + -18c + 80 + c2 = 0 + 80

Reorder the terms:
-80 + 80 + -18c + c2 = 0 + 80

Combine like terms: -80 + 80 = 0
0 + -18c + c2 = 0 + 80
-18c + c2 = 0 + 80

Combine like terms: 0 + 80 = 80
-18c + c2 = 80

The c term is -18c.  Take half its coefficient (-9).
Square it (81) and add it to both sides.

Add '81' to each side of the equation.
-18c + 81 + c2 = 80 + 81

Reorder the terms:
81 + -18c + c2 = 80 + 81

Combine like terms: 80 + 81 = 161
81 + -18c + c2 = 161

Factor a perfect square on the left side:
(c + -9)(c + -9) = 161

Calculate the square root of the right side: 12.68857754

Break this problem into two subproblems by setting 
(c + -9) equal to 12.68857754 and -12.68857754.

Subproblem 1

c + -9 = 12.68857754 Simplifying c + -9 = 12.68857754 Reorder the terms: -9 + c = 12.68857754 Solving -9 + c = 12.68857754 Solving for variable 'c'. Move all terms containing c to the left, all other terms to the right. Add '9' to each side of the equation. -9 + 9 + c = 12.68857754 + 9 Combine like terms: -9 + 9 = 0 0 + c = 12.68857754 + 9 c = 12.68857754 + 9 Combine like terms: 12.68857754 + 9 = 21.68857754 c = 21.68857754 Simplifying c = 21.68857754

Subproblem 2

c + -9 = -12.68857754 Simplifying c + -9 = -12.68857754 Reorder the terms: -9 + c = -12.68857754 Solving -9 + c = -12.68857754 Solving for variable 'c'. Move all terms containing c to the left, all other terms to the right. Add '9' to each side of the equation. -9 + 9 + c = -12.68857754 + 9 Combine like terms: -9 + 9 = 0 0 + c = -12.68857754 + 9 c = -12.68857754 + 9 Combine like terms: -12.68857754 + 9 = -3.68857754 c = -3.68857754 Simplifying c = -3.68857754

Solution

The solution to the problem is based on the solutions from the subproblems. c = {21.68857754, -3.68857754}

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