25.42=3.14(r^2)

Solution for 25.42=3.14(r^2) equation:

Simplifying
25.42 = 3.14(r2)

Solving
25.42 = 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.
25.42 + -3.14r2 = 3.14r2 + -3.14r2

Combine like terms: 3.14r2 + -3.14r2 = 0.00
25.42 + -3.14r2 = 0.00

Add '-25.42' to each side of the equation.
25.42 + -25.42 + -3.14r2 = 0.00 + -25.42

Combine like terms: 25.42 + -25.42 = 0.00
0.00 + -3.14r2 = 0.00 + -25.42
-3.14r2 = 0.00 + -25.42

Combine like terms: 0.00 + -25.42 = -25.42
-3.14r2 = -25.42

Divide each side by '-3.14'.
r2 = 8.095541401

Simplifying
r2 = 8.095541401

Take the square root of each side:
r = {-2.84526649, 2.84526649}