[tex]\cfrac{7}{11-3x}[/tex] <---- for what values of "x" is the denominator 0, that is
what value of "x" makes the denominator 0?
for, if the denominator is zero, then the fraction is "undefined", can't divide by 0
and THAT VALUE, is not a value "x" can take, thus not in the domain,
since "x" is the "input", and thus the domain
so, in short, to bore you to death, the values "x" can take will be anything, [tex]x\in \mathbb{R}[/tex], BUT that value