Question

How many horizontal tangent lines does f(x) have?

A. 0
B. 1
C. 2
D. 3
E. 4

Answer 1

C. 2

Explanation:

Whenever the tangent line to a point on the graph is horizontal that indicates there is a zero instantaneous change, or in other words it's not increasing or decreasing at that certain point which would indicate a turning point.

So horizontal tangent lines only occur at turning points for the most part or whenever the graph is for some reason having a zero slope.

As shown by the graph there are two turning points meaning there should be two horizontal tangent lines.