# How do you calculate log_3 -4.8 with a calculator?

Assuming that you want to take the $\log$ of $- 4.8$ to the base $3$, this expression is mathematically invalid.
It is impossible to take the $\log$ of $x$ where $x \le 0$. This is because, for any non-zero constant, $x$, there is no power we can raise it to so that it becomes equal to or less than $0$.