we know that
the formula to calculate teh slope between two points is equal to
[tex]m=\frac{(y2-y1)}{(x2-x1)}[/tex]where
(x1,y1) is one point
and
(x2,y2) is the other point
substitute the values in the formula and solve for m
Example
you have the points
(1,4) and (3,2)
so
(x1,y1)=(1,4)
(x2,y2)=(3,2)
substitute in te formula
m=(2-4)/(3-1)
m=-2/2
m=-1
the slope is -1