r^2+8r-2=0

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Solution for r^2+8r-2=0 equation:


Simplifying
r2 + 8r + -2 = 0

Reorder the terms:
-2 + 8r + r2 = 0

Solving
-2 + 8r + r2 = 0

Solving for variable 'r'.

Begin completing the square.

Move the constant term to the right:

Add '2' to each side of the equation.
-2 + 8r + 2 + r2 = 0 + 2

Reorder the terms:
-2 + 2 + 8r + r2 = 0 + 2

Combine like terms: -2 + 2 = 0
0 + 8r + r2 = 0 + 2
8r + r2 = 0 + 2

Combine like terms: 0 + 2 = 2
8r + r2 = 2

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 = 2 + 16

Reorder the terms:
16 + 8r + r2 = 2 + 16

Combine like terms: 2 + 16 = 18
16 + 8r + r2 = 18

Factor a perfect square on the left side:
(r + 4)(r + 4) = 18

Calculate the square root of the right side: 4.242640687

Break this problem into two subproblems by setting 
(r + 4) equal to 4.242640687 and -4.242640687.

Subproblem 1

r + 4 = 4.242640687 Simplifying r + 4 = 4.242640687 Reorder the terms: 4 + r = 4.242640687 Solving 4 + r = 4.242640687 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 = 4.242640687 + -4 Combine like terms: 4 + -4 = 0 0 + r = 4.242640687 + -4 r = 4.242640687 + -4 Combine like terms: 4.242640687 + -4 = 0.242640687 r = 0.242640687 Simplifying r = 0.242640687

Subproblem 2

r + 4 = -4.242640687 Simplifying r + 4 = -4.242640687 Reorder the terms: 4 + r = -4.242640687 Solving 4 + r = -4.242640687 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 = -4.242640687 + -4 Combine like terms: 4 + -4 = 0 0 + r = -4.242640687 + -4 r = -4.242640687 + -4 Combine like terms: -4.242640687 + -4 = -8.242640687 r = -8.242640687 Simplifying r = -8.242640687

Solution

The solution to the problem is based on the solutions from the subproblems. r = {0.242640687, -8.242640687}

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