-r^2s^2+81=

Solution for -r^2s^2+81= equation:

Simplifying
-1r2s2 + 81 = 0

Reorder the terms:
81 + -1r2s2 = 0

Solving
81 + -1r2s2 = 0

Solving for variable 'r'.

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

Add '-81' to each side of the equation.
81 + -81 + -1r2s2 = 0 + -81

Combine like terms: 81 + -81 = 0
0 + -1r2s2 = 0 + -81
-1r2s2 = 0 + -81

Combine like terms: 0 + -81 = -81
-1r2s2 = -81

Divide each side by '-1s2'.
r2 = 81s-2

Simplifying
r2 = 81s-2

Take the square root of each side:
r = {-9s-1, 9s-1}