7850=3.14*r^2

Solution for 7850=3.14*r^2 equation:

Simplifying
7850 = 3.14r2

Solving
7850 = 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.
7850 + -3.14r2 = 3.14r2 + -3.14r2

Combine like terms: 3.14r2 + -3.14r2 = 0.00
7850 + -3.14r2 = 0.00

Add '-7850' to each side of the equation.
7850 + -7850 + -3.14r2 = 0.00 + -7850

Combine like terms: 7850 + -7850 = 0
0 + -3.14r2 = 0.00 + -7850
-3.14r2 = 0.00 + -7850

Combine like terms: 0.00 + -7850 = -7850
-3.14r2 = -7850

Divide each side by '-3.14'.
r2 = 2500

Simplifying
r2 = 2500

Take the square root of each side:
r = {-50, 50}