r^2+18r=11

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Solution for r^2+18r=11 equation:


Simplifying
r2 + 18r = 11

Reorder the terms:
18r + r2 = 11

Solving
18r + r2 = 11

Solving for variable 'r'.

Reorder the terms:
-11 + 18r + r2 = 11 + -11

Combine like terms: 11 + -11 = 0
-11 + 18r + r2 = 0

Begin completing the square.

Move the constant term to the right:

Add '11' to each side of the equation.
-11 + 18r + 11 + r2 = 0 + 11

Reorder the terms:
-11 + 11 + 18r + r2 = 0 + 11

Combine like terms: -11 + 11 = 0
0 + 18r + r2 = 0 + 11
18r + r2 = 0 + 11

Combine like terms: 0 + 11 = 11
18r + r2 = 11

The r term is 18r.  Take half its coefficient (9).
Square it (81) and add it to both sides.

Add '81' to each side of the equation.
18r + 81 + r2 = 11 + 81

Reorder the terms:
81 + 18r + r2 = 11 + 81

Combine like terms: 11 + 81 = 92
81 + 18r + r2 = 92

Factor a perfect square on the left side:
(r + 9)(r + 9) = 92

Calculate the square root of the right side: 9.591663047

Break this problem into two subproblems by setting 
(r + 9) equal to 9.591663047 and -9.591663047.

Subproblem 1

r + 9 = 9.591663047 Simplifying r + 9 = 9.591663047 Reorder the terms: 9 + r = 9.591663047 Solving 9 + r = 9.591663047 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '-9' to each side of the equation. 9 + -9 + r = 9.591663047 + -9 Combine like terms: 9 + -9 = 0 0 + r = 9.591663047 + -9 r = 9.591663047 + -9 Combine like terms: 9.591663047 + -9 = 0.591663047 r = 0.591663047 Simplifying r = 0.591663047

Subproblem 2

r + 9 = -9.591663047 Simplifying r + 9 = -9.591663047 Reorder the terms: 9 + r = -9.591663047 Solving 9 + r = -9.591663047 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '-9' to each side of the equation. 9 + -9 + r = -9.591663047 + -9 Combine like terms: 9 + -9 = 0 0 + r = -9.591663047 + -9 r = -9.591663047 + -9 Combine like terms: -9.591663047 + -9 = -18.591663047 r = -18.591663047 Simplifying r = -18.591663047

Solution

The solution to the problem is based on the solutions from the subproblems. r = {0.591663047, -18.591663047}

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