Question 1128412
<pre>We plot the two points and draw the line:

{{{drawing(400,4400/17,-8,9,-6,5,grid(1),

graph(400,4400/17,-8,9,-6,5), line(-6,-4,7,-5))}}}

We draw a horizontal green line from the left point until it is
exactly above the right point, like this:

{{{drawing(400,4400/17,-8,9,-6,5,grid(1),
green(line(-6,-4,7,-4)),
graph(400,4400/17,-8,9,-6,5), line(-6,-4,7,-5))}}}

We count the number of units which is the length of the green line.
We count 13.  That number is called the RUN.

We draw a red vertical line from the right end of the green line
down to the line that we want to find the slope of, like this:

{{{drawing(400,4400/17,-8,9,-6,5,grid(1),graph(400,4400/17,-8,9,-6,5),
green(line(-6,-4,7,-4)),red(line(7,-4,7,-5)),
 line(-6,-4,7,-5))}}}

We count the number of units which is the length of the red line.
We count only 1 unit.  But since it goes DOWN from the green line to the
given line, we make it NEGATIVE.  So it is -1. That number -1 is called 
the RISE.

The definition of slope is {{{SLOPE=RISE/RUN=(-1)/13=-1/13}}}

Edwin</pre>