Question 144534
There are 4 4th roots.  You show 2 of them.
There are 2 square roots of 81, 9 and -9.  Each of these has 2 square roots.  3 and -3 are the square roots of +9.

The other 2:
{{{x^2 = -9}}}
{{{x^2+9=0}}}
*[invoke solve_quadratic_equation 1,0,9]