#### Answer

The linear function is
$$f(x)=-\frac{2}{3}x-1.$$

#### Work Step by Step

The equation of the linear function passing through points $P(x_1,y_1)$ and $Q(x_2,y_2)$ is given by
$$y=\frac{y_2-y_1}{x_2-x_1}(x-x_1)+y_1.$$
Using the value from the problem $x_1=0,\quad y_1=-1,\quad x_2=3,\quad y_2=-3$
we get
$$y=\frac{-3-(-1)}{3-0}(x-0)+(-1)$$
which gives
$$y=-\frac{2}{3}x-1,$$
so the linear functon is $$f(x)=-\frac{2}{3}x-1.$$