.
a. Find the slope of the line which passes through the points

and

.
b. Write an expression, in terms of

, for the slope of the
line passing through

and

. Simplify your
expression.
c. Suppose that you
evaluated your expression from part (b) for a value of

that is really close to zero. What
would your answer be really close to?
d. In calculus terms, what are you
finding in part (c) of this problem?