k^2+6k-81=0

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Solution for k^2+6k-81=0 equation:


Simplifying
k2 + 6k + -81 = 0

Reorder the terms:
-81 + 6k + k2 = 0

Solving
-81 + 6k + k2 = 0

Solving for variable 'k'.

Begin completing the square.

Move the constant term to the right:

Add '81' to each side of the equation.
-81 + 6k + 81 + k2 = 0 + 81

Reorder the terms:
-81 + 81 + 6k + k2 = 0 + 81

Combine like terms: -81 + 81 = 0
0 + 6k + k2 = 0 + 81
6k + k2 = 0 + 81

Combine like terms: 0 + 81 = 81
6k + k2 = 81

The k term is 6k.  Take half its coefficient (3).
Square it (9) and add it to both sides.

Add '9' to each side of the equation.
6k + 9 + k2 = 81 + 9

Reorder the terms:
9 + 6k + k2 = 81 + 9

Combine like terms: 81 + 9 = 90
9 + 6k + k2 = 90

Factor a perfect square on the left side:
(k + 3)(k + 3) = 90

Calculate the square root of the right side: 9.486832981

Break this problem into two subproblems by setting 
(k + 3) equal to 9.486832981 and -9.486832981.

Subproblem 1

k + 3 = 9.486832981 Simplifying k + 3 = 9.486832981 Reorder the terms: 3 + k = 9.486832981 Solving 3 + k = 9.486832981 Solving for variable 'k'. Move all terms containing k to the left, all other terms to the right. Add '-3' to each side of the equation. 3 + -3 + k = 9.486832981 + -3 Combine like terms: 3 + -3 = 0 0 + k = 9.486832981 + -3 k = 9.486832981 + -3 Combine like terms: 9.486832981 + -3 = 6.486832981 k = 6.486832981 Simplifying k = 6.486832981

Subproblem 2

k + 3 = -9.486832981 Simplifying k + 3 = -9.486832981 Reorder the terms: 3 + k = -9.486832981 Solving 3 + k = -9.486832981 Solving for variable 'k'. Move all terms containing k to the left, all other terms to the right. Add '-3' to each side of the equation. 3 + -3 + k = -9.486832981 + -3 Combine like terms: 3 + -3 = 0 0 + k = -9.486832981 + -3 k = -9.486832981 + -3 Combine like terms: -9.486832981 + -3 = -12.486832981 k = -12.486832981 Simplifying k = -12.486832981

Solution

The solution to the problem is based on the solutions from the subproblems. k = {6.486832981, -12.486832981}

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