00:01
So i want to find the first four terms.
00:03
So we're actually going to use something that we have established already before.
00:09
So we've got that 1 plus x, 1 over 1 plus x, is equal to 1 minus x squared, minus x to the third, and so on.
00:22
So then 1 over 1 plus x squared is equal to 1 minus x squared plus x squared plus x to the fourth, minus x to the 6th.
00:35
Per substitution of x squared in for x.
00:41
So, or the other way, actually, take x squared and plug it into x here.
00:47
That's how we get the resulting values.
00:51
All right.
00:52
So then that means that that's the summation from k equals zero to infinity of x to the 2k times negative 1 to the k...