assuming this is a linear function
find slope
slope=changey/changex
so from x=3, y=5 and x=5, y=-3
change in y is -8
change in x is 2
so -8/2=-4
slope is -4
y=mx+b
m=slope
input -4 for m
y=-4x+b
sub a point
x=3 and y=5
5=-4(3)+b
5=-12+b
add 12
17=b
y=-4x+17
when x=0,
y=-4(0)+17
y=0+17
y=17
y=17 when x=0
