00:01
Here, we're given a sign chart of the first and second derivatives of a function, and we're asked to find the local max and minns and inflection points.
00:11
So what i like to do is instead of seeing the plus and minuses, i like to draw an up arrow or down arrow, because if the derivative is negative, that means the function is decreasing.
00:24
So instead of negative, i'm just going to write a down arrow.
00:27
And for a plus sign, i'm going to draw an up arrow.
00:30
And then i'll just do that in each of these regions.
00:34
And that makes it very easy to see, hey, x1 is a minimum.
00:37
Goes down and comes back up.
00:40
So there's a minimum at x1.
00:44
Then if i look at x2, well, nothing happens there.
00:47
I go up and i continue going up.
00:48
I don't see anything.
00:50
Same thing at x3.
00:52
And then finally at x4, it's a maximum.
00:59
So those are our only max and mince...