Given the function, find it's domain.

$\displaystyle {f{{\left({x}\right)}}}=\frac{{{6}{x}+{5}}}{{{x}^{{2}}-{6}{x}+{8}}}$

The domain is all real numbers except $\displaystyle {x}=$ 

If there is more than one answer, write it as a list, using commas to separate your answers.