## Precalculus (6th Edition) Blitzer

The domain of the given function is $\left( -\infty ,6 \right)$.
We know that the domain is a set of values of x at which: $f(x)=\ln (6-x)$ We know that, $(6-x)>0$ Therefore, $-x>-6$ Or it can be written as $x<6$ Thus, the domain of the given function is $\left( -\infty ,6 \right)$.