Find the slope of the line containing the given pair of points. If the line is undefined, state so. Please be sure to show all of your work.
(1, 2) and (9, 12)
There are several ways.
One is with slope.
The slope of the line between those two points is:
(12-2)/(9-1)
= 10/8
= 5/4
Now the slope between some other point (x,y) on the line and one of the original points (I pick the first one) is the same:
(y-2)/(x-1) = 5/4
5 x - 5 = 4 y - 8
4y = 5 x + 3
y = (5/4) x + 3/4