00:01
You want to sketch the graph above a function, f of x, and we've been told these three things about it, that first of all it's increasing, its derivative is decreasing, and its integral is also decreasing.
00:17
So let's remind ourselves what decreasing and increasing even mean, right? they're all statements about the derivative of that function.
00:24
Remember that saying that f is decreasing, excuse me, f is increasing, what's the number? what that means is that f prime is positive, right? that is literally what it means for a function f to be increasing.
00:38
And similarly, for a function to be decreasing, well, that just means that its derivative, in this case f double prime, is negative.
00:47
And the same thing can be said for a.
00:49
We know that its derivative must be negative.
00:53
And since a is the integral of f, the derivative of a is f.
00:58
So i've translated these three statements into a slightly different format that personally i find easier to understand.
01:04
We're trying to sketch a graph of a function f which satisfies these three things.
01:09
It has to be negative.
01:11
Its first derivative has to be positive, and its second derivative has to be negative.
01:18
So let's try and sketch something like that.
01:23
So first of all, it has to be negative...