This may look like an afterthought, since I'm sticking it at the end, but, it isn't.  This stuff is really important -- I just didn't want to interrupt the flow of the zeros lessons.

Check out this graph:

a graph

You've got an ant climbing on the graph.  Not just any ant...  Pierre the Mountain Climbing Ant!

Pierre the Mountain Climbing Ant!!

(He's kind of a pathetic math superhero.)  For this, the rule is that Pierre only crawls from let to right (like we read):

Pierre always walks from left to right

If Pierre is climbing uphill, then the graph is increasing:

on the intervals ( -infinity , -3 ) and ( 1 , 4 ) , Pierre is climbing uphill ... therefore, the graph is increasing

So, our graph is increasing on

( -infinity, -3 ) U ( 1 , 4 )

(we use interval notation with X VALUES!)