$(1$ point$)$ Let $f(x)=\frac{5}{5-9x}.$

Then the slope of the tangent line to the graph of $y=f(x)$ at the point $(,-\frac{5}{4})$

is the limit as $x$ tends to $q,$ of the following expression

$$

The value of this limit is

It follows that the equation of the tangent line is $y=4$