Question 147363
Do you mean solve for f(x)? The equation is already solved for f(x). I'm assuming that you want to solve for x




{{{f(x)=x^2-9}}} Start with the given equation



{{{0=(x+3)(x-3)}}} Plug in {{{f(x)=0}}}



{{{0=(x+3)(x-3)}}} Factor the right side 



Now set each factor equal to zero:


{{{x+3=0}}} or  {{{x-3=0}}} 



{{{x=-3}}} or  {{{x=3}}}    Now solve for x in each case



So our answers are 


 {{{x=-3}}} or  {{{x=3}}}