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

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


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

Reorder the terms for easier multiplication:
2 * 3.14 * 12r + 2(3.14) * r2 = 1356

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

Multiply 6.28 * 12
75.36r + 2(3.14) * r2 = 1356

Multiply 2 * 3.14
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}

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