A linear function can be written in this form:
y - y2 = m(x - x2)
f(-3) = 2
f(-3) is saying that some function had the number -3 put in for the value of x. The output was a value of 2. Which is our y. So we have a coordinate point of:
(-3, 2)
Same thing with f(1) = 0
(1,0)
Now we need to find the slope, m.
(2 - 0) / (-3 - 1) = 2 / -4 = -1/2
So an equation for the linear function f is this:
y - 2 = -1/2(x + 3)
(Note that the -3 we subbed in has become a positive 3 because the equation called for a negative. And two negatives become a positive)