r^2-8r-79=6

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Solution for r^2-8r-79=6 equation:


Simplifying
r2 + -8r + -79 = 6

Reorder the terms:
-79 + -8r + r2 = 6

Solving
-79 + -8r + r2 = 6

Solving for variable 'r'.

Reorder the terms:
-79 + -6 + -8r + r2 = 6 + -6

Combine like terms: -79 + -6 = -85
-85 + -8r + r2 = 6 + -6

Combine like terms: 6 + -6 = 0
-85 + -8r + r2 = 0

Begin completing the square.

Move the constant term to the right:

Add '85' to each side of the equation.
-85 + -8r + 85 + r2 = 0 + 85

Reorder the terms:
-85 + 85 + -8r + r2 = 0 + 85

Combine like terms: -85 + 85 = 0
0 + -8r + r2 = 0 + 85
-8r + r2 = 0 + 85

Combine like terms: 0 + 85 = 85
-8r + r2 = 85

The r term is -8r.  Take half its coefficient (-4).
Square it (16) and add it to both sides.

Add '16' to each side of the equation.
-8r + 16 + r2 = 85 + 16

Reorder the terms:
16 + -8r + r2 = 85 + 16

Combine like terms: 85 + 16 = 101
16 + -8r + r2 = 101

Factor a perfect square on the left side:
(r + -4)(r + -4) = 101

Calculate the square root of the right side: 10.049875621

Break this problem into two subproblems by setting 
(r + -4) equal to 10.049875621 and -10.049875621.

Subproblem 1

r + -4 = 10.049875621 Simplifying r + -4 = 10.049875621 Reorder the terms: -4 + r = 10.049875621 Solving -4 + r = 10.049875621 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '4' to each side of the equation. -4 + 4 + r = 10.049875621 + 4 Combine like terms: -4 + 4 = 0 0 + r = 10.049875621 + 4 r = 10.049875621 + 4 Combine like terms: 10.049875621 + 4 = 14.049875621 r = 14.049875621 Simplifying r = 14.049875621

Subproblem 2

r + -4 = -10.049875621 Simplifying r + -4 = -10.049875621 Reorder the terms: -4 + r = -10.049875621 Solving -4 + r = -10.049875621 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '4' to each side of the equation. -4 + 4 + r = -10.049875621 + 4 Combine like terms: -4 + 4 = 0 0 + r = -10.049875621 + 4 r = -10.049875621 + 4 Combine like terms: -10.049875621 + 4 = -6.049875621 r = -6.049875621 Simplifying r = -6.049875621

Solution

The solution to the problem is based on the solutions from the subproblems. r = {14.049875621, -6.049875621}

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