00:01
X to the fourth we want to find the derivative f prime of x by finding the limit of this difference quotient as h goes towards zero so we need to take f of x plus h well f of x is x to the fourth so f of x plus h will be x plus h to the fourth then we have to subtract f of x which is x to the fourth then we have to put that over h.
00:47
And we have to take the limit of this.
00:50
Let me squeeze it in here.
00:51
I forgot to write it in.
00:52
We have to take the limit of this quotient as h goes towards zero.
00:59
So we need to take the limit of x plus h to the fourth minus x to the fourth, divided by h as h goes towards zero.
01:07
So we're going to expand l x plus h to the fourth.
01:16
Okay, so x plus h to the fourth expands out to be this entire expression from x to the fourth all the way down to plus h to the fourth.
01:28
And then we still have to subtract x to the fourth.
01:31
So we wrote it here and we have to put that all over h.
01:34
And we need to take the limit of this entire expression as h goes towards zero.
01:45
Now we could do a little bit of canceling, not a whole lot.
01:49
X to the fourth minus x to the fourth cancels.
01:54
So we are going to take the limit as h approaches zero of this entire expression over h.
02:06
Now, i'm going to factor out of these terms in the numerator, the greatest common factor, which would be just h.
02:18
So out of the numerator, we're going to factor out in h.
02:22
So h times 4x cubed.
02:29
That would give you to 4x cubed h plus...