The Muddiest Point in Chapter Four

What was the muddiest point in this chapter?  The muddiest point is something that you don't understand or fully grasp.  It can be a term, a concept, a formula.

An example would be:

"The difference between a logarithmic and exponential equation.  I don't know how to tell the two apart."

There are two ways to earn these points:

1. Post your own Muddiest Point.  That is worth 5 points. Then answer someone else's Muddiest Point for the remaining 5 points.

2. If you don't have a Muddiest Point, to earn 10 points answer the Muddiest Point of two (2) of your peers.  These must be two different topics.  Teach them what you know and clear the mud!