2r^2-2r-1=0

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Solution for 2r^2-2r-1=0 equation:


Simplifying
2r2 + -2r + -1 = 0

Reorder the terms:
-1 + -2r + 2r2 = 0

Solving
-1 + -2r + 2r2 = 0

Solving for variable 'r'.

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

Divide each side by '2'.
-0.5 + -1r + r2 = 0

Move the constant term to the right:

Add '0.5' to each side of the equation.
-0.5 + -1r + 0.5 + r2 = 0 + 0.5

Reorder the terms:
-0.5 + 0.5 + -1r + r2 = 0 + 0.5

Combine like terms: -0.5 + 0.5 = 0.0
0.0 + -1r + r2 = 0 + 0.5
-1r + r2 = 0 + 0.5

Combine like terms: 0 + 0.5 = 0.5
-1r + r2 = 0.5

The r term is -1r.  Take half its coefficient (-0.5).
Square it (0.25) and add it to both sides.

Add '0.25' to each side of the equation.
-1r + 0.25 + r2 = 0.5 + 0.25

Reorder the terms:
0.25 + -1r + r2 = 0.5 + 0.25

Combine like terms: 0.5 + 0.25 = 0.75
0.25 + -1r + r2 = 0.75

Factor a perfect square on the left side:
(r + -0.5)(r + -0.5) = 0.75

Calculate the square root of the right side: 0.866025404

Break this problem into two subproblems by setting 
(r + -0.5) equal to 0.866025404 and -0.866025404.

Subproblem 1

r + -0.5 = 0.866025404 Simplifying r + -0.5 = 0.866025404 Reorder the terms: -0.5 + r = 0.866025404 Solving -0.5 + r = 0.866025404 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '0.5' to each side of the equation. -0.5 + 0.5 + r = 0.866025404 + 0.5 Combine like terms: -0.5 + 0.5 = 0.0 0.0 + r = 0.866025404 + 0.5 r = 0.866025404 + 0.5 Combine like terms: 0.866025404 + 0.5 = 1.366025404 r = 1.366025404 Simplifying r = 1.366025404

Subproblem 2

r + -0.5 = -0.866025404 Simplifying r + -0.5 = -0.866025404 Reorder the terms: -0.5 + r = -0.866025404 Solving -0.5 + r = -0.866025404 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '0.5' to each side of the equation. -0.5 + 0.5 + r = -0.866025404 + 0.5 Combine like terms: -0.5 + 0.5 = 0.0 0.0 + r = -0.866025404 + 0.5 r = -0.866025404 + 0.5 Combine like terms: -0.866025404 + 0.5 = -0.366025404 r = -0.366025404 Simplifying r = -0.366025404

Solution

The solution to the problem is based on the solutions from the subproblems. r = {1.366025404, -0.366025404}

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