Answer
$y=-3x+6$
Work Step by Step
The point-slope form between two points is given by $ m= \dfrac{y_2-y_1}{x_2-x_1}$
Plug in the given data.
$ m= \dfrac{-3-3}{3-1}=-3$
Now, the point-slope equation is:
$ y-y_1= m (x-x_1)$ becomes:
$ y-3=-3(x-1)$
Which simplifies to:
$y=-3x+6$
