Find the gradients of the straight lines joining each of the following sets of points.

a) (−3,−6) and (2, −1)

b) (4, −6) and (1, 0)

c) (5, −7) and (−3, 9)

d)  (−8, −3) and (2, −7)

e) (−3k, −4k) and (−k, 6k) 

f) (4q, −4q) and (7q, 8q)