x-intercept=4;passes through (-1,3)

x-intercept = 4 ---> we have a point (4,0)

so slope = (3-0/(-1-4) = -3/5

y = (-3/5)x + b
(4,0) on it

0 = (-3/5)(4) + b
12/5 = b

y =(-3/5)x + 12/5