r^2-4r=-1

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Solution for r^2-4r=-1 equation:


Simplifying
r2 + -4r = -1

Reorder the terms:
-4r + r2 = -1

Solving
-4r + r2 = -1

Solving for variable 'r'.

Reorder the terms:
1 + -4r + r2 = -1 + 1

Combine like terms: -1 + 1 = 0
1 + -4r + r2 = 0

Begin completing the square.

Move the constant term to the right:

Add '-1' to each side of the equation.
1 + -4r + -1 + r2 = 0 + -1

Reorder the terms:
1 + -1 + -4r + r2 = 0 + -1

Combine like terms: 1 + -1 = 0
0 + -4r + r2 = 0 + -1
-4r + r2 = 0 + -1

Combine like terms: 0 + -1 = -1
-4r + r2 = -1

The r term is -4r.  Take half its coefficient (-2).
Square it (4) and add it to both sides.

Add '4' to each side of the equation.
-4r + 4 + r2 = -1 + 4

Reorder the terms:
4 + -4r + r2 = -1 + 4

Combine like terms: -1 + 4 = 3
4 + -4r + r2 = 3

Factor a perfect square on the left side:
(r + -2)(r + -2) = 3

Calculate the square root of the right side: 1.732050808

Break this problem into two subproblems by setting 
(r + -2) equal to 1.732050808 and -1.732050808.

Subproblem 1

r + -2 = 1.732050808 Simplifying r + -2 = 1.732050808 Reorder the terms: -2 + r = 1.732050808 Solving -2 + r = 1.732050808 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '2' to each side of the equation. -2 + 2 + r = 1.732050808 + 2 Combine like terms: -2 + 2 = 0 0 + r = 1.732050808 + 2 r = 1.732050808 + 2 Combine like terms: 1.732050808 + 2 = 3.732050808 r = 3.732050808 Simplifying r = 3.732050808

Subproblem 2

r + -2 = -1.732050808 Simplifying r + -2 = -1.732050808 Reorder the terms: -2 + r = -1.732050808 Solving -2 + r = -1.732050808 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '2' to each side of the equation. -2 + 2 + r = -1.732050808 + 2 Combine like terms: -2 + 2 = 0 0 + r = -1.732050808 + 2 r = -1.732050808 + 2 Combine like terms: -1.732050808 + 2 = 0.267949192 r = 0.267949192 Simplifying r = 0.267949192

Solution

The solution to the problem is based on the solutions from the subproblems. r = {3.732050808, 0.267949192}

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