00:01
Okay, so we're looking at this function that is x to the fourth minus 4x cubed.
00:10
And i actually have some good algebra two students that are pretty good about knowing the behavior, n behavior of a graph.
00:19
So we know that the function is going to be decreasing at first just based off the end behavior, and then somewhere in between here.
00:27
But you can actually figure out where, by taking the derivative, which would be 4x cubed minus 12x squared and setting it equal to zero because a function is decreasing when it's derivative is less than zero.
00:45
So i would probably factor out of 4x squared in this problem.
00:49
You'd be left with x minus 3 is equal to zero.
00:53
Now the fact that this x equals zero it actually has a multiplicity of two, so if you made a sign chart for this and you picked out zero and three, it actually goes from, like, if you plugged in a negative or a positive value there, it doesn't matter.
01:17
It's always going to be positive.
01:18
X squared is always positive.
01:22
But if you plugged in negative three or negative four, negative whatever, you're going to get a negative on this side...