k^2+2k-86=-9

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Solution for k^2+2k-86=-9 equation:


Simplifying
k2 + 2k + -86 = -9

Reorder the terms:
-86 + 2k + k2 = -9

Solving
-86 + 2k + k2 = -9

Solving for variable 'k'.

Reorder the terms:
-86 + 9 + 2k + k2 = -9 + 9

Combine like terms: -86 + 9 = -77
-77 + 2k + k2 = -9 + 9

Combine like terms: -9 + 9 = 0
-77 + 2k + k2 = 0

Begin completing the square.

Move the constant term to the right:

Add '77' to each side of the equation.
-77 + 2k + 77 + k2 = 0 + 77

Reorder the terms:
-77 + 77 + 2k + k2 = 0 + 77

Combine like terms: -77 + 77 = 0
0 + 2k + k2 = 0 + 77
2k + k2 = 0 + 77

Combine like terms: 0 + 77 = 77
2k + k2 = 77

The k term is 2k.  Take half its coefficient (1).
Square it (1) and add it to both sides.

Add '1' to each side of the equation.
2k + 1 + k2 = 77 + 1

Reorder the terms:
1 + 2k + k2 = 77 + 1

Combine like terms: 77 + 1 = 78
1 + 2k + k2 = 78

Factor a perfect square on the left side:
(k + 1)(k + 1) = 78

Calculate the square root of the right side: 8.831760866

Break this problem into two subproblems by setting 
(k + 1) equal to 8.831760866 and -8.831760866.

Subproblem 1

k + 1 = 8.831760866 Simplifying k + 1 = 8.831760866 Reorder the terms: 1 + k = 8.831760866 Solving 1 + k = 8.831760866 Solving for variable 'k'. Move all terms containing k to the left, all other terms to the right. Add '-1' to each side of the equation. 1 + -1 + k = 8.831760866 + -1 Combine like terms: 1 + -1 = 0 0 + k = 8.831760866 + -1 k = 8.831760866 + -1 Combine like terms: 8.831760866 + -1 = 7.831760866 k = 7.831760866 Simplifying k = 7.831760866

Subproblem 2

k + 1 = -8.831760866 Simplifying k + 1 = -8.831760866 Reorder the terms: 1 + k = -8.831760866 Solving 1 + k = -8.831760866 Solving for variable 'k'. Move all terms containing k to the left, all other terms to the right. Add '-1' to each side of the equation. 1 + -1 + k = -8.831760866 + -1 Combine like terms: 1 + -1 = 0 0 + k = -8.831760866 + -1 k = -8.831760866 + -1 Combine like terms: -8.831760866 + -1 = -9.831760866 k = -9.831760866 Simplifying k = -9.831760866

Solution

The solution to the problem is based on the solutions from the subproblems. k = {7.831760866, -9.831760866}

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