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The DTFT of the given signal
x[n] = 1 ^{– n} u[– n – 1]
2

1. e^jΩ
  2 – e^{– jΩ}
2. 2e^jΩ
  2 – e^{– jΩ}
3. e^jΩ
  2 – e^jΩ
4. 2e^jΩ
  2 – e^jΩ

Correct Option: C

	_∞
X(e^jΩ) =		x[n].e^–jΩn
	^{n = – ∞}

	_∞
=		(1/2)^-nu[- n - 1]e^–jΩn
	^{n = – ∞}	2

	_∞
=		(1/2)^-ne^–jΩn
	^{n = – ∞}	2

	_∞
=		(1/2e^jΩn)^-n
	^{n = – ∞}	2

			₀		_∞		_∞
=		∵		a^k =		(1/a)^k =		(a)^-k
		∵	^{k = ∞}		^{k = 0}		^{k = 0}

=	e^jΩ
	2

	1 -	e^jΩ
		2

=	e^jΩ
	2 - e^jΩ