Explanation:
that is also called slope or inclination or change rate.
it is the ratio y change / x change.
when going from point 1 to point 2 (the sequence is not important for the final end result, but once you picked one, you need to keep it the same for x and y), we get
x changes by -5 (from 3 to -2).
y changes by -5 (from 8 to 3).
so it is
-5/-5 = 1/1 = 1