r^2-2r-79=0

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Solution for r^2-2r-79=0 equation:


Simplifying
r2 + -2r + -79 = 0

Reorder the terms:
-79 + -2r + r2 = 0

Solving
-79 + -2r + r2 = 0

Solving for variable 'r'.

Begin completing the square.

Move the constant term to the right:

Add '79' to each side of the equation.
-79 + -2r + 79 + r2 = 0 + 79

Reorder the terms:
-79 + 79 + -2r + r2 = 0 + 79

Combine like terms: -79 + 79 = 0
0 + -2r + r2 = 0 + 79
-2r + r2 = 0 + 79

Combine like terms: 0 + 79 = 79
-2r + r2 = 79

The r term is -2r.  Take half its coefficient (-1).
Square it (1) and add it to both sides.

Add '1' to each side of the equation.
-2r + 1 + r2 = 79 + 1

Reorder the terms:
1 + -2r + r2 = 79 + 1

Combine like terms: 79 + 1 = 80
1 + -2r + r2 = 80

Factor a perfect square on the left side:
(r + -1)(r + -1) = 80

Calculate the square root of the right side: 8.94427191

Break this problem into two subproblems by setting 
(r + -1) equal to 8.94427191 and -8.94427191.

Subproblem 1

r + -1 = 8.94427191 Simplifying r + -1 = 8.94427191 Reorder the terms: -1 + r = 8.94427191 Solving -1 + r = 8.94427191 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '1' to each side of the equation. -1 + 1 + r = 8.94427191 + 1 Combine like terms: -1 + 1 = 0 0 + r = 8.94427191 + 1 r = 8.94427191 + 1 Combine like terms: 8.94427191 + 1 = 9.94427191 r = 9.94427191 Simplifying r = 9.94427191

Subproblem 2

r + -1 = -8.94427191 Simplifying r + -1 = -8.94427191 Reorder the terms: -1 + r = -8.94427191 Solving -1 + r = -8.94427191 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '1' to each side of the equation. -1 + 1 + r = -8.94427191 + 1 Combine like terms: -1 + 1 = 0 0 + r = -8.94427191 + 1 r = -8.94427191 + 1 Combine like terms: -8.94427191 + 1 = -7.94427191 r = -7.94427191 Simplifying r = -7.94427191

Solution

The solution to the problem is based on the solutions from the subproblems. r = {9.94427191, -7.94427191}

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