Find the slope of the line joining the points?

Question

(a,b),(b,a)

I know that the answer is -1, I just have no idea how to get it

Please explain, Thanks a bunch! = )

Answer 1

Isn't the slope just the second y minus the first y divided by the second x minus the first x?

So, wouldn't the slope be just (a-b)/(b-a)?

Isn't that just -1?

Answer 2

Slope is rise/run, or (change in Y)/(change in X).

This would be:

slope = (b-a)/(a-b)

From that, it should be fairly obvious that (b-a) has the same magnitude but opposite sign of (a-b).  Since that is the case, your slope is -1, no matter what a and b are.

Example:

If a is 5 and b is 7:

slope = (7-5)/(5-7)

slope = (2)/(-2) = -1