11r^2-2r-8=0

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Solution for 11r^2-2r-8=0 equation:


Simplifying
11r2 + -2r + -8 = 0

Reorder the terms:
-8 + -2r + 11r2 = 0

Solving
-8 + -2r + 11r2 = 0

Solving for variable 'r'.

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

Divide each side by '11'.
-0.7272727273 + -0.1818181818r + r2 = 0

Move the constant term to the right:

Add '0.7272727273' to each side of the equation.
-0.7272727273 + -0.1818181818r + 0.7272727273 + r2 = 0 + 0.7272727273

Reorder the terms:
-0.7272727273 + 0.7272727273 + -0.1818181818r + r2 = 0 + 0.7272727273

Combine like terms: -0.7272727273 + 0.7272727273 = 0.0000000000
0.0000000000 + -0.1818181818r + r2 = 0 + 0.7272727273
-0.1818181818r + r2 = 0 + 0.7272727273

Combine like terms: 0 + 0.7272727273 = 0.7272727273
-0.1818181818r + r2 = 0.7272727273

The r term is -0.1818181818r.  Take half its coefficient (-0.0909090909).
Square it (0.008264462808) and add it to both sides.

Add '0.008264462808' to each side of the equation.
-0.1818181818r + 0.008264462808 + r2 = 0.7272727273 + 0.008264462808

Reorder the terms:
0.008264462808 + -0.1818181818r + r2 = 0.7272727273 + 0.008264462808

Combine like terms: 0.7272727273 + 0.008264462808 = 0.735537190108
0.008264462808 + -0.1818181818r + r2 = 0.735537190108

Factor a perfect square on the left side:
(r + -0.0909090909)(r + -0.0909090909) = 0.735537190108

Calculate the square root of the right side: 0.857634648

Break this problem into two subproblems by setting 
(r + -0.0909090909) equal to 0.857634648 and -0.857634648.

Subproblem 1

r + -0.0909090909 = 0.857634648 Simplifying r + -0.0909090909 = 0.857634648 Reorder the terms: -0.0909090909 + r = 0.857634648 Solving -0.0909090909 + r = 0.857634648 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '0.0909090909' to each side of the equation. -0.0909090909 + 0.0909090909 + r = 0.857634648 + 0.0909090909 Combine like terms: -0.0909090909 + 0.0909090909 = 0.0000000000 0.0000000000 + r = 0.857634648 + 0.0909090909 r = 0.857634648 + 0.0909090909 Combine like terms: 0.857634648 + 0.0909090909 = 0.9485437389 r = 0.9485437389 Simplifying r = 0.9485437389

Subproblem 2

r + -0.0909090909 = -0.857634648 Simplifying r + -0.0909090909 = -0.857634648 Reorder the terms: -0.0909090909 + r = -0.857634648 Solving -0.0909090909 + r = -0.857634648 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '0.0909090909' to each side of the equation. -0.0909090909 + 0.0909090909 + r = -0.857634648 + 0.0909090909 Combine like terms: -0.0909090909 + 0.0909090909 = 0.0000000000 0.0000000000 + r = -0.857634648 + 0.0909090909 r = -0.857634648 + 0.0909090909 Combine like terms: -0.857634648 + 0.0909090909 = -0.7667255571 r = -0.7667255571 Simplifying r = -0.7667255571

Solution

The solution to the problem is based on the solutions from the subproblems. r = {0.9485437389, -0.7667255571}

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