00:01
Ok, so in this exercise we have our function f of x equal to x to the fourth power minus 50 x squared plus 2.
00:11
Ok, let's find the derivative.
00:13
Well the derivative is 4 x cubed minus 100 x and this derivative can be written as 4 x multiplied by x squared minus 25.
00:29
Perfect.
00:29
Now let me draw a sine chart for f prime.
00:34
This is gonna be easy.
00:36
We are gonna have three critical points, zero, negative 5 and 5.
00:44
Perfect.
00:45
Now as we can see our function f prime is gonna be positive here, negative here, positive here and negative here again.
00:58
Perfect.
00:59
So this shows that f is increasing where f prime is positive.
01:07
So on negative 5, 0 union 5, infinity.
01:14
Decreasing where f prime is negative, so on the interval negative infinity negative 5 union 0, 5.
01:24
Moreover, f has a local max at x equal to 0.
01:39
Ok, at x equal to 0 only and let me write max here.
01:47
Ok, so local max at x equal to 0 and two local minima at x equal to negative 5 and 5...