00:01
For this problem, we have a chart that shows the amount of air pollution removed by trees in chicago month by month throughout the year.
00:09
As you can see, there are five different graphs superimposed here on this chart, one showing ozone, particulates, no2, s -o -2, and co.
00:21
So, first of all, are these curves the graphs of functions? are they functions? well, in order to be functions, it means every input has exactly one output.
00:34
Otherwise, known as the vertical test.
00:36
Can you draw a vertical line anywhere? if you draw a vertical line and you touch more than two points on the same graph, that is not a function.
00:45
If you try that here, though, you'll see that it is a function.
00:50
Every vertical line only touches at most one point on each of these five graphs.
00:56
So yes, these are functions.
00:58
Now, in particular, let's look at the graph for particulates.
01:03
What is it doing? where is it increasing, decreasing, or staying constant? well, from january to about april, it is flat.
01:13
It's quite low on our graph here, under 50, so it is constant.
01:20
What happens in april? well, in april, it starts to rise.
01:24
It increases very steeply, has a little bit where it's still rising, but just not quite as much...