The table below shows three values of $x$ and their corresponding values of $g(x)$, where $g(x)=\frac{f(x)}{x+1}$ and $f(x)$ is a linear function.

x	g(x)
1	6
4	3.6
9	2.8

What is the slope of the graph of $y=f(x)$ in the $xy$-plane?