r^2+2r-11=0

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


Simplifying
r2 + 2r + -11 = 0

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

Solving
-11 + 2r + r2 = 0

Solving for variable 'r'.

Begin completing the square.

Move the constant term to the right:

Add '11' to each side of the equation.
-11 + 2r + 11 + r2 = 0 + 11

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

Combine like terms: -11 + 11 = 0
0 + 2r + r2 = 0 + 11
2r + r2 = 0 + 11

Combine like terms: 0 + 11 = 11
2r + r2 = 11

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 = 11 + 1

Reorder the terms:
1 + 2r + r2 = 11 + 1

Combine like terms: 11 + 1 = 12
1 + 2r + r2 = 12

Factor a perfect square on the left side:
(r + 1)(r + 1) = 12

Calculate the square root of the right side: 3.464101615

Break this problem into two subproblems by setting 
(r + 1) equal to 3.464101615 and -3.464101615.

Subproblem 1

r + 1 = 3.464101615 Simplifying r + 1 = 3.464101615 Reorder the terms: 1 + r = 3.464101615 Solving 1 + r = 3.464101615 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 = 3.464101615 + -1 Combine like terms: 1 + -1 = 0 0 + r = 3.464101615 + -1 r = 3.464101615 + -1 Combine like terms: 3.464101615 + -1 = 2.464101615 r = 2.464101615 Simplifying r = 2.464101615

Subproblem 2

r + 1 = -3.464101615 Simplifying r + 1 = -3.464101615 Reorder the terms: 1 + r = -3.464101615 Solving 1 + r = -3.464101615 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 = -3.464101615 + -1 Combine like terms: 1 + -1 = 0 0 + r = -3.464101615 + -1 r = -3.464101615 + -1 Combine like terms: -3.464101615 + -1 = -4.464101615 r = -4.464101615 Simplifying r = -4.464101615

Solution

The solution to the problem is based on the solutions from the subproblems. r = {2.464101615, -4.464101615}

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