Question 731676
Here is a guess that you do not mean what you wrote but mean this instead:


f(x)=(3x^2)/(x^2-49) as text
OR
{{{f(x)=(3x^2)/(x^2-49)}}} in rendered typesetting.


The important restriction on the function is that {{{x<>-7}}} and {{{x<>+7}}}.  The reason is that either of those values would make the denominator zero.  The domain of f(x) is these three intervals:

(-infinity, -7)
(-7, +7)
(+7, +infinity).