2((3.14)r^2)+(2(3.14)r)12=1356

Solution for 2((3.14)r^2)+(2(3.14)r)12=1356 equation:

Simplifying
2((3.14) * r2) + (2(3.14) * r) * 12 = 1356

Remove parenthesis around (3.14r2)
2 * 3.14r2 + (2(3.14) * r) * 12 = 1356

Multiply 2 * 3.14
6.28r2 + (2(3.14) * r) * 12 = 1356

Multiply 2 * 3.14
6.28r2 + (6.28r) * 12 = 1356

Remove parenthesis around (6.28r)
6.28r2 + 6.28r * 12 = 1356

Reorder the terms for easier multiplication:
6.28r2 + 6.28 * 12r = 1356

Multiply 6.28 * 12
6.28r2 + 75.36r = 1356

Reorder the terms:
75.36r + 6.28r2 = 1356

Solving
75.36r + 6.28r2 = 1356

Solving for variable 'r'.

Reorder the terms:
-1356 + 75.36r + 6.28r2 = 1356 + -1356

Combine like terms: 1356 + -1356 = 0
-1356 + 75.36r + 6.28r2 = 0

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

Divide each side by '6.28'.
-215.9235669 + 12r + r2 = 0

Move the constant term to the right:

Add '215.9235669' to each side of the equation.
-215.9235669 + 12r + 215.9235669 + r2 = 0 + 215.9235669

Reorder the terms:
-215.9235669 + 215.9235669 + 12r + r2 = 0 + 215.9235669

Combine like terms: -215.9235669 + 215.9235669 = 0.0000000
0.0000000 + 12r + r2 = 0 + 215.9235669
12r + r2 = 0 + 215.9235669

Combine like terms: 0 + 215.9235669 = 215.9235669
12r + r2 = 215.9235669

The r term is 12r.  Take half its coefficient (6).
Square it (36) and add it to both sides.

Add '36' to each side of the equation.
12r + 36 + r2 = 215.9235669 + 36

Reorder the terms:
36 + 12r + r2 = 215.9235669 + 36

Combine like terms: 215.9235669 + 36 = 251.9235669
36 + 12r + r2 = 251.9235669

Factor a perfect square on the left side:
(r + 6)(r + 6) = 251.9235669

Calculate the square root of the right side: 15.872100267

Break this problem into two subproblems by setting 
(r + 6) equal to 15.872100267 and -15.872100267.

Subproblem 1
r + 6 = 15.872100267

Simplifying
r + 6 = 15.872100267

Reorder the terms:
6 + r = 15.872100267

Solving
6 + r = 15.872100267

Solving for variable 'r'.

Move all terms containing r to the left, all other terms to the right.

Add '-6' to each side of the equation.
6 + -6 + r = 15.872100267 + -6

Combine like terms: 6 + -6 = 0
0 + r = 15.872100267 + -6
r = 15.872100267 + -6

Combine like terms: 15.872100267 + -6 = 9.872100267
r = 9.872100267

Simplifying
r = 9.872100267

Subproblem 2
r + 6 = -15.872100267

Simplifying
r + 6 = -15.872100267

Reorder the terms:
6 + r = -15.872100267

Solving
6 + r = -15.872100267

Solving for variable 'r'.

Move all terms containing r to the left, all other terms to the right.

Add '-6' to each side of the equation.
6 + -6 + r = -15.872100267 + -6

Combine like terms: 6 + -6 = 0
0 + r = -15.872100267 + -6
r = -15.872100267 + -6

Combine like terms: -15.872100267 + -6 = -21.872100267
r = -21.872100267

Simplifying
r = -21.872100267

Solution
The solution to the problem is based on the solutions
from the subproblems.
r = {9.872100267, -21.872100267}