k^2-2k-7=0

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Solution for k^2-2k-7=0 equation:


Simplifying
k2 + -2k + -7 = 0

Reorder the terms:
-7 + -2k + k2 = 0

Solving
-7 + -2k + k2 = 0

Solving for variable 'k'.

Begin completing the square.

Move the constant term to the right:

Add '7' to each side of the equation.
-7 + -2k + 7 + k2 = 0 + 7

Reorder the terms:
-7 + 7 + -2k + k2 = 0 + 7

Combine like terms: -7 + 7 = 0
0 + -2k + k2 = 0 + 7
-2k + k2 = 0 + 7

Combine like terms: 0 + 7 = 7
-2k + k2 = 7

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 = 7 + 1

Reorder the terms:
1 + -2k + k2 = 7 + 1

Combine like terms: 7 + 1 = 8
1 + -2k + k2 = 8

Factor a perfect square on the left side:
(k + -1)(k + -1) = 8

Calculate the square root of the right side: 2.828427125

Break this problem into two subproblems by setting 
(k + -1) equal to 2.828427125 and -2.828427125.

Subproblem 1

k + -1 = 2.828427125 Simplifying k + -1 = 2.828427125 Reorder the terms: -1 + k = 2.828427125 Solving -1 + k = 2.828427125 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 = 2.828427125 + 1 Combine like terms: -1 + 1 = 0 0 + k = 2.828427125 + 1 k = 2.828427125 + 1 Combine like terms: 2.828427125 + 1 = 3.828427125 k = 3.828427125 Simplifying k = 3.828427125

Subproblem 2

k + -1 = -2.828427125 Simplifying k + -1 = -2.828427125 Reorder the terms: -1 + k = -2.828427125 Solving -1 + k = -2.828427125 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 = -2.828427125 + 1 Combine like terms: -1 + 1 = 0 0 + k = -2.828427125 + 1 k = -2.828427125 + 1 Combine like terms: -2.828427125 + 1 = -1.828427125 k = -1.828427125 Simplifying k = -1.828427125

Solution

The solution to the problem is based on the solutions from the subproblems. k = {3.828427125, -1.828427125}

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