Power series expansions - which is imossible

[razored]

Which of the following expansions is impossible?

a \sqrt{x-1} in powers of x

b \sqrt{x+1} in powers of x

c ln(x) in powers of (x-1)

d tanx in powers of (x-\pi / 4 )

e ln(1-x) in powers of x

What are htey asking and how do i do this? the answer is A by the way

 

[Mark44]

"In powers of (x - a)" means that x will be close to a, and that the function and its derivatives will be evaluated at a. Which of the functions above are defined at a (which will be 0, or 1, or pi/4 in these problems)?

 

[razored]

So for a, x=0, and that is an imaginary result. Is this the same thing as saying it is centered around a?

Thank you.

 

[Mark44]

So for a, x=0, and that is an imaginary result. Is this the same thing as saying it is centered around a?

Thank you.

If a = 0, it is.