Question 400194
Use a substitution, let {{{u^2=x}}}, {{{u=sqrt(x)}}}
{{{(u^2-9)/(u-3)=((u-3)(u+3))/(u-3)}}}
{{{(u^2-9)/(u-3)=u+3}}}
{{{(x-9)/(sqrt(x)-3)=sqrt(x)+3}}}