121=81r^2

Solution for 121=81r^2 equation:

Simplifying
121 = 81r2

Solving
121 = 81r2

Solving for variable 'r'.

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

Add '-81r2' to each side of the equation.
121 + -81r2 = 81r2 + -81r2

Combine like terms: 81r2 + -81r2 = 0
121 + -81r2 = 0

Add '-121' to each side of the equation.
121 + -121 + -81r2 = 0 + -121

Combine like terms: 121 + -121 = 0
0 + -81r2 = 0 + -121
-81r2 = 0 + -121

Combine like terms: 0 + -121 = -121
-81r2 = -121

Divide each side by '-81'.
r2 = 1.49382716

Simplifying
r2 = 1.49382716

Take the square root of each side:
r = {-1.222222222, 1.222222222}