MHB Is This the Correct Laurent Series Expansion for $\frac{1}{z^3-z^4}$?

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The discussion focuses on verifying the correctness of a Laurent series expansion for the function $\frac{1}{z^3-z^4}$ in the region where $0<|z|<1$. The proposed solution involves rewriting the function as $\frac{1}{z^3(1-z)}$ and expanding it using a geometric series. The resulting series is expressed as $\sum_{n=0}^{\infty}z^{n-3}$. The response confirms that the solution is correct. The discussion concludes with a positive affirmation of the proposed expansion.
aruwin
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Hello.
Can you check if my answer is correct please?

For the region ${\{z\inℂ\big|0<|z|<1\}}$, expand $\frac{1}{z^3-z^4}$ that has a center z=0 into Laurent series.

My solution:
$$\frac{1}{z^3(1-z)}=\frac{1}{z^3}\sum_{n=0}^{\infty}z^n=\sum_{n=0}^{\infty}z^{n-3}$$
 
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aruwin said:
Hello.
Can you check if my answer is correct please?

For the region ${\{z\inℂ\big|0<|z|<1\}}$, expand $\frac{1}{z^3-z^4}$ that has a center z=0 into Laurent series.

My solution:
$$\frac{1}{z^3(1-z)}=\frac{1}{z^3}\sum_{n=0}^{\infty}z^n=\sum_{n=0}^{\infty}z^{n-3}$$

Yes, all right!...

Kind regards

$\chi$ $\sigma$
 

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