Question 462835
{{{f(x)=12/X^2+22x+105}}}
When you have to find domain, think about any values that x cannot be.  Since you have a rational function (a fraction with variables in it), there are some values x cannot be.  Remember that the denominator of a fraction can never be zero.  What number makes the bottom of the fraction be zero?  Take the entire denominator of the fraction and set it equal to zero and see.
{{{x^2=0}}}
{{{x=0}}} This is the only value x cannot be in this function.  There fore the domain is everything EXCEPT x=0.  This can be written different ways:
{{{x<>0}}}
{{{-infinity<x<0}}} and {{{0<x<infinity}}}
(-infinity,0) (0,infinity)