188.4=3.14*r*10+3.14*r^2

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Solution for 188.4=3.14*r*10+3.14*r^2 equation:


Simplifying
188.4 = 3.14r * 10 + 3.14r2

Reorder the terms for easier multiplication:
188.4 = 3.14 * 10r + 3.14r2

Multiply 3.14 * 10
188.4 = 31.4r + 3.14r2

Solving
188.4 = 31.4r + 3.14r2

Solving for variable 'r'.

Reorder the terms:
188.4 + -31.4r + -3.14r2 = 31.4r + -31.4r + 3.14r2 + -3.14r2

Combine like terms: 31.4r + -31.4r = 0.0
188.4 + -31.4r + -3.14r2 = 0.0 + 3.14r2 + -3.14r2
188.4 + -31.4r + -3.14r2 = 3.14r2 + -3.14r2

Combine like terms: 3.14r2 + -3.14r2 = 0.00
188.4 + -31.4r + -3.14r2 = 0.00

Begin completing the square.  Divide all terms by
-3.14 the coefficient of the squared term: 

Divide each side by '-3.14'.
-60 + 10r + r2 = 0

Move the constant term to the right:

Add '60' to each side of the equation.
-60 + 10r + 60 + r2 = 0 + 60

Reorder the terms:
-60 + 60 + 10r + r2 = 0 + 60

Combine like terms: -60 + 60 = 0
0 + 10r + r2 = 0 + 60
10r + r2 = 0 + 60

Combine like terms: 0 + 60 = 60
10r + r2 = 60

The r term is 10r.  Take half its coefficient (5).
Square it (25) and add it to both sides.

Add '25' to each side of the equation.
10r + 25 + r2 = 60 + 25

Reorder the terms:
25 + 10r + r2 = 60 + 25

Combine like terms: 60 + 25 = 85
25 + 10r + r2 = 85

Factor a perfect square on the left side:
(r + 5)(r + 5) = 85

Calculate the square root of the right side: 9.219544457

Break this problem into two subproblems by setting 
(r + 5) equal to 9.219544457 and -9.219544457.

Subproblem 1

r + 5 = 9.219544457 Simplifying r + 5 = 9.219544457 Reorder the terms: 5 + r = 9.219544457 Solving 5 + r = 9.219544457 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '-5' to each side of the equation. 5 + -5 + r = 9.219544457 + -5 Combine like terms: 5 + -5 = 0 0 + r = 9.219544457 + -5 r = 9.219544457 + -5 Combine like terms: 9.219544457 + -5 = 4.219544457 r = 4.219544457 Simplifying r = 4.219544457

Subproblem 2

r + 5 = -9.219544457 Simplifying r + 5 = -9.219544457 Reorder the terms: 5 + r = -9.219544457 Solving 5 + r = -9.219544457 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '-5' to each side of the equation. 5 + -5 + r = -9.219544457 + -5 Combine like terms: 5 + -5 = 0 0 + r = -9.219544457 + -5 r = -9.219544457 + -5 Combine like terms: -9.219544457 + -5 = -14.219544457 r = -14.219544457 Simplifying r = -14.219544457

Solution

The solution to the problem is based on the solutions from the subproblems. r = {4.219544457, -14.219544457}

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