Cracking The Ap Calculus ab Exam 2018

The formula for the slope   of  the secant  line    is

Remember    this    formula!    This    is  called  the Difference  Quotient.

While   at  first   the Difference  Quotient    may seem    like    another

formula to  memorize,   keep    in  mind    that    it’s    just    another way of

writing the slope   formula.

The Secant and the Tangent

As you can see, the farther apart the two points are, the less the slope of the line corresponds to the slope
of the curve.

Conversely, the closer the two points are, the more accurate the approximation is.