r^2+2r=47

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Solution for r^2+2r=47 equation:


Simplifying
r2 + 2r = 47

Reorder the terms:
2r + r2 = 47

Solving
2r + r2 = 47

Solving for variable 'r'.

Reorder the terms:
-47 + 2r + r2 = 47 + -47

Combine like terms: 47 + -47 = 0
-47 + 2r + r2 = 0

Begin completing the square.

Move the constant term to the right:

Add '47' to each side of the equation.
-47 + 2r + 47 + r2 = 0 + 47

Reorder the terms:
-47 + 47 + 2r + r2 = 0 + 47

Combine like terms: -47 + 47 = 0
0 + 2r + r2 = 0 + 47
2r + r2 = 0 + 47

Combine like terms: 0 + 47 = 47
2r + r2 = 47

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 = 47 + 1

Reorder the terms:
1 + 2r + r2 = 47 + 1

Combine like terms: 47 + 1 = 48
1 + 2r + r2 = 48

Factor a perfect square on the left side:
(r + 1)(r + 1) = 48

Calculate the square root of the right side: 6.92820323

Break this problem into two subproblems by setting 
(r + 1) equal to 6.92820323 and -6.92820323.

Subproblem 1

r + 1 = 6.92820323 Simplifying r + 1 = 6.92820323 Reorder the terms: 1 + r = 6.92820323 Solving 1 + r = 6.92820323 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 = 6.92820323 + -1 Combine like terms: 1 + -1 = 0 0 + r = 6.92820323 + -1 r = 6.92820323 + -1 Combine like terms: 6.92820323 + -1 = 5.92820323 r = 5.92820323 Simplifying r = 5.92820323

Subproblem 2

r + 1 = -6.92820323 Simplifying r + 1 = -6.92820323 Reorder the terms: 1 + r = -6.92820323 Solving 1 + r = -6.92820323 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 = -6.92820323 + -1 Combine like terms: 1 + -1 = 0 0 + r = -6.92820323 + -1 r = -6.92820323 + -1 Combine like terms: -6.92820323 + -1 = -7.92820323 r = -7.92820323 Simplifying r = -7.92820323

Solution

The solution to the problem is based on the solutions from the subproblems. r = {5.92820323, -7.92820323}

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