00:01
To start this problem, we're going to calculate the first three derivatives of 1 over x squared, and then we're going to figure out what those values are at a, and plug them into the formula for the taylor series and find a general form.
00:16
So if we start with the function 1 over x squared, 1 over x squared is equivalent to x to the negative 2 power.
00:26
If we take the first derivative of x to the negative 2, we can use the power rule, bring the exponent to the front times x, subtract 1 from the exponent, negative 2, x to negative 3.
00:38
Second derivative, following the same manner, it would be negative 2 times negative 3, 6x to the negative 4, and then f triple prime of 3 will be negative 4 times 6, which is negative 24, x to the negative 5.
00:57
Now if we plug in a, which is 1, to each of these, we get f of 1 is 1 to the negative 2, which is just 1, since 1 raise to any exponent is just 1.
01:08
The first derivative at 1, it would be negative 2 times 1 to the negative 3, which is just negative 2.
01:16
Second derivative at 1 will be 6 times 1 to the 4th, which is just 6.
01:23
And then the third derivative evaluated at 1, be negative 24.
01:28
Times 1 to the negative 5th, which is negative 24.
01:33
Now we're going to plug these into the taylor series definition, which starts with f of a, which is 1, plus f prime of a, which is negative 2.
01:45
This will be 1 minus 2 times x minus a, which is 1, plus f double prime at a, which is 6 over 2 factorial times x minus 1, squared.
02:00
Minus 24 over 3 factorial times x minus 1 cubed and so on.
02:10
And here we can see that we have somewhat of a general pattern.
02:15
Since we can write this in some notation using k equals 0 to infinity, the coefficients are 1 to 6 over 2 factorial.
02:27
2 factorial is 2 times 1 is just 2.
02:30
6 divided by 2 is 3, 24 over 3 factorial is 24 over 3 times 2 times 1.
02:43
Cancelling out a factor of 2 and the top and bottom, leave us 12 in the numerator.
02:49
It will be 12 divided by 3, which is 4.
02:52
So this coefficient is 4, and this is 3.
02:57
So the coefficient is just increasing 1 and vary negative sign...