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Rational discrete system functions.
Considering
the function

when is
the pole of order 1 { ( <
1) is the assumption } ,
is a pole of order 1 ( >1)
.
Now considering
the Inverse transform of
we have ,
as | z | =1
is contained in the ROC and <1,
hence the only possible option for inverse is .
Similarly for
the function
( since >1and
| z | =1 is contained in the ROC of
the function )
Therefore,
The contribution of
is a right sided exponentially decaying term (possibly
multiplied by a polynomial in n
if the order of pole >1 ) |
The contribution of
is a left sided exponentially decaying term ( possibly
multipled by a polynomial in n
if the order of the pole >1 ) |
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αnu[n]
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-(βnu[-n-1])
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