# Partial Fraction Expansion (Inverse Z-Transform)

1. Nov 20, 2011

### ElfenKiller

1. The problem statement, all variables and given/known data

$H(z) = \frac{6-z^{-1}}{1+0.5z^{-1}} + \frac{2}{1-0.4z^{-1}} = k + \frac{A}{1+0.5z^{-1}} + \frac{2}{1-0.4z^{-1}}$

where $A = (6-z^{-1})$ is evaluated at $z^{-1}=-2$.

2. Relevant equations

Partial fraction expansion.

3. The attempt at a solution

Why is $z^{-1}$ set equal to -2? I thought normally you use the terms in the denominators for $z^{-1}$ ...

2. Nov 20, 2011

### vela

Staff Emeritus
What do you mean by "use the terms in the denominator for $z^{-1}$"? Use them how?

3. Nov 20, 2011

### ElfenKiller

Like here: http://dspcan.homestead.com/files/Ztran/zinvpart.htm" [Broken]

Last edited by a moderator: May 5, 2017
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