We have the next table
x y
0 3
1 -1
2 -5
First, we have the value of y in x=0 that is y=3, so that gives us the y-intercept that is 3, then we need to find the slope using two points of the table
(0 3)=(x1,y1)
(1 -1)=(x2,y2)
the function rule will have the next form
y=mx+b,
where m is the slope and b the y-intercept,
if we substitute the values we obtain the function rule, that is