39.25=3.14r^2

Solution for 39.25=3.14r^2 equation:

Simplifying
39.25 = 3.14r2

Solving
39.25 = 3.14r2

Solving for variable 'r'.

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

Add '-3.14r2' to each side of the equation.
39.25 + -3.14r2 = 3.14r2 + -3.14r2

Combine like terms: 3.14r2 + -3.14r2 = 0.00
39.25 + -3.14r2 = 0.00

Add '-39.25' to each side of the equation.
39.25 + -39.25 + -3.14r2 = 0.00 + -39.25

Combine like terms: 39.25 + -39.25 = 0.00
0.00 + -3.14r2 = 0.00 + -39.25
-3.14r2 = 0.00 + -39.25

Combine like terms: 0.00 + -39.25 = -39.25
-3.14r2 = -39.25

Divide each side by '-3.14'.
r2 = 12.5

Simplifying
r2 = 12.5

Take the square root of each side:
r = {-3.535533906, 3.535533906}