Question 792473
{{{ f(x)= 3^log( 9, x ) }}} is a fancy way of expressing {{{ f(x)= sqrt(x)}}}
{{{ f(x)= 3^log(9,x)=(9^0.5)^log(9,x)=9^((0.5*log(9,x)))=(9^log(9,x))^0.5=x^0.5=sqrt(x)}}}
To figure out the inverse function, we switch the x and y, then solve for y:
The inverse of {{{y=sqrt(x)}}} is given by 
{{{x=sqrt(y)}}} ---> {{{highlight(y=x^2)}}}