-r^2=r-1

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


Simplifying
-1r2 = r + -1

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

Solving
-1r2 = -1 + r

Solving for variable 'r'.

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

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

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

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

Begin completing the square.  Divide all terms by
-1 the coefficient of the squared term: 

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

Move the constant term to the right:

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

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

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

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

The r term is r.  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.
 + 0.25 + r2 = 1 + 0.25

Combine like terms:  + 0.25 = 1.25
1.25 + r2 = 1 + 0.25

Combine like terms: 1 + 0.25 = 1.25
1.25 + r2 = 1.25

Factor a perfect square on the left side:
(r + 0.5)(r + 0.5) = 1.25

Calculate the square root of the right side: 1.118033989

Break this problem into two subproblems by setting 
(r + 0.5) equal to 1.118033989 and -1.118033989.

Subproblem 1

r + 0.5 = 1.118033989 Simplifying r + 0.5 = 1.118033989 Reorder the terms: 0.5 + r = 1.118033989 Solving 0.5 + r = 1.118033989 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 = 1.118033989 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + r = 1.118033989 + -0.5 r = 1.118033989 + -0.5 Combine like terms: 1.118033989 + -0.5 = 0.618033989 r = 0.618033989 Simplifying r = 0.618033989

Subproblem 2

r + 0.5 = -1.118033989 Simplifying r + 0.5 = -1.118033989 Reorder the terms: 0.5 + r = -1.118033989 Solving 0.5 + r = -1.118033989 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 = -1.118033989 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + r = -1.118033989 + -0.5 r = -1.118033989 + -0.5 Combine like terms: -1.118033989 + -0.5 = -1.618033989 r = -1.618033989 Simplifying r = -1.618033989

Solution

The solution to the problem is based on the solutions from the subproblems. r = {0.618033989, -1.618033989}

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