Residue of $\frac{1}{(1-z)^3}$ at $z=1$

118 Views Asked by At

I know there is a singularity of $z=1$ but I am a bit confused on how to find the residue at that point since if we have that $f(z)=\frac{g(z)}{h(z)}$ with $g(z)=1$ and $h(z)=(1-z)^3$ then $g(z)$ has a zero of order 0 (no zero) and $h(z)$ has a zero of order 3 since its first and second derivatives vanish at $z=1$ but the third derivative does not vanish at $z=1$. That is all I have, any help would be appreciated!

1

There are 1 best solutions below

8
On BEST ANSWER

What is the Laurent series for $f(z)$ in powers of $z-1$? (Hint: it's easy!) What is the coefficient of $(z-1)^{-1}$ in this series?