00:01
All right, on this problem, we've been given an original function and looks something like this.
00:09
It's like it goes up and then takes a little bit of a stop, goes up, takes a little bit of a stop, and then so on.
00:16
Now, what we're wanting to do here is find the graph that represents the derivative of this function, the derivative of this function.
00:29
First time it stops is at about two, and it stops until what looks like to be about three and a half.
00:35
So from two, the three and a half here, it stops.
00:38
Now, because from 2 to 3 .5, it doesn't do anything at all.
00:43
It means its derivative is 0.
00:45
So from 2 to about 3 .5 for the derivative, the derivative is zero there.
00:52
Okay, because it just stalled out there, the derivative is zero there.
00:57
Now, it's a similar for these next points here.
00:59
Somewhere between right there and somewhere there on the end.
01:04
So it means similarly between about 4 .5 to 7.
01:14
And from 9 to 10.
01:15
About 4 .5 to 7 and 9 to 10.
01:17
The derivative should be zero.
01:18
So it's going to need to be on this x -axis quite a bit here, okay, quite a bit, which most of ours are.
01:28
Okay, but you can automatically get rid of d because it doesn't do that.
01:34
Everywhere else, it's positive.
01:35
The derivative is, this slope is always positive.
01:38
So since that slope is always positive, it means the derivative is always positive.
01:42
Okay, the derivative is always positive.
01:44
So the derivative should always be up here somewhere, okay, because it's always positive.
01:47
Always got to be positive, which means you can automatically throw out b, f, and e.
01:57
B, f, and e.
01:58
It only leaves us with a and c.
02:01
You'll notice on a, it doesn't stay zero for very long there on a.
02:06
It doesn't really hover at zero very much...