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Power series expansions - which is imossible

  • Thread starter razored
  • Start date
  • #1
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Which of the following expansions is impossible?

a [tex]\sqrt{x-1}[/tex] in powers of x

b [tex]\sqrt{x+1}[/tex] in powers of x

c [tex]ln(x)[/tex] in powers of (x-1)

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

e [tex]ln(1-x)[/tex] in powers of x

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

Answers and Replies

  • #2
33,170
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"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)?
 
  • #3
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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.
 
  • #4
33,170
4,857


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.
 

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