Question 1152492
 {{{f(x)=(x^2+x-12)/(x^2-9)}}}

 {{{f(x)=((x + 4) (x - 3))/((x-3)(x+3))}}}

The domain of a rational function consists of all the real numbers {{{x }}}except those for which the denominator is {{{0}}} . 

so,{{{(x-3)(x+3)=0}}} if {{{x=3}}} and {{{x=-3}}}

both values are excluded from a domain

domain is:

{ {{{x}}} element {{{R }}}: {{{x<>-3}}} and {{{x<>3}}} }