12.56=3.14r^2

Solution for 12.56=3.14r^2 equation:

Simplifying
12.56 = 3.14r2

Solving
12.56 = 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.
12.56 + -3.14r2 = 3.14r2 + -3.14r2

Combine like terms: 3.14r2 + -3.14r2 = 0.00
12.56 + -3.14r2 = 0.00

Add '-12.56' to each side of the equation.
12.56 + -12.56 + -3.14r2 = 0.00 + -12.56

Combine like terms: 12.56 + -12.56 = 0.00
0.00 + -3.14r2 = 0.00 + -12.56
-3.14r2 = 0.00 + -12.56

Combine like terms: 0.00 + -12.56 = -12.56
-3.14r2 = -12.56

Divide each side by '-3.14'.
r2 = 4

Simplifying
r2 = 4

Take the square root of each side:
r = {-2, 2}