81r^2-16=0

Solution for 81r^2-16=0 equation:

Simplifying
81r2 + -16 = 0

Reorder the terms:
-16 + 81r2 = 0

Solving
-16 + 81r2 = 0

Solving for variable 'r'.

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

Add '16' to each side of the equation.
-16 + 16 + 81r2 = 0 + 16

Combine like terms: -16 + 16 = 0
0 + 81r2 = 0 + 16
81r2 = 0 + 16

Combine like terms: 0 + 16 = 16
81r2 = 16

Divide each side by '81'.
r2 = 0.1975308642

Simplifying
r2 = 0.1975308642

Take the square root of each side:
r = {-0.444444444, 0.444444444}