0=r^2-10.89

Solution for 0=r^2-10.89 equation:

Simplifying
0 = r2 + -10.89

Reorder the terms:
0 = -10.89 + r2

Solving
0 = -10.89 + r2

Solving for variable 'r'.

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

Add '-1r2' to each side of the equation.
0 + -1r2 = -10.89 + r2 + -1r2
Remove the zero:
-1r2 = -10.89 + r2 + -1r2

Combine like terms: r2 + -1r2 = 0
-1r2 = -10.89 + 0
-1r2 = -10.89

Divide each side by '-1'.
r2 = 10.89

Simplifying
r2 = 10.89

Take the square root of each side:
r = {-3.3, 3.3}