Monday, 11 November 2013

complex analysis - Laurent series expansion of f(z)=frac1(z1)2(z+1)2

Let f(z)=1(z1)2(z+1)2. While trying to expand this function into the Laurent series, convergent in P(0,1,2):={zC:1<|z|<2}, a few questions popped into my mind.




  1. We can write f(z)=14(1(z1)2+1(z+1)2). Both functions inside parentheses are complex derivatives of functions which have immediate Laurent series expansion: 11z and 1z+1. Now, can we differentiate the obtained series term by term to get the desired expansion of f? If so, is it because the Laurent series is convergent almost uniformly?

  2. Could someone verify that the Laurent series of f is convergent in P(0,1,)?


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