What is the inverse z-transform of X(z)= 1/(1-1.5z-1+0.5z-2) if ROC is...
Explanation: The partial fraction expansion for the given X(z) is
X(z)= 2z/(z-1)-z/(z-0.5)
In case when ROC is |z|<0.5,the signal is anti causal. Thus both the terms in the above equation are anti causal terms. So, if we apply inverse z-transform to the above equation we get x(n)= [-2+0.5n]u(-n-1).
View all questions of this test
What is the inverse z-transform of X(z)= 1/(1-1.5z-1+0.5z-2) if ROC is...
> First, we need to factor the denominator of X(z):
>
> X(z) = 1 / (1 - 1.5z^-1 + 0.5z^-2)
>
> X(z) = 1 / [(1 - z^-1)(1 - 0.5z^-1)]
>
> Now, we can use the partial fraction expansion to express X(z) as a sum of simpler terms:
>
> X(z) = A/(1 - z^-1) + B/(1 - 0.5z^-1)
>
> where A and B are constants to be determined. To find A and B, we can multiply both sides of this equation by the denominators of the two terms on the right-hand side:
>
> X(z)(1 - z^-1)(1 - 0.5z^-1) = A(1 - 0.5z^-1) + B(1 - z^-1)
>
> Next, we can substitute z = 0.5 and z = 1 in this equation to get two equations in A and B:
>
> X(0.5)(1 - 0.5^-1)(1 - 0.5^-1) = A(1 - 0.5^-1) + B(1 - 0.5)
>
> X(1)(1 - 1^-1)(1 - 0.5^-1) = A(1 - 0.5) + B(1 - 1^-1)
>
> Simplifying these equations, we get:
>
> A + B = X(0.5)(1 - 0.5^-1)(1 - 0.5^-1) = 4/3
>
> 0.5A + B = X(1)(1 - 0.5) + B = 2/3
>
> Solving for A and B, we get:
>
> A = 2/3
>
> B = 2/3 - X(1)(1 - 0.5) = -2/3
>
> So, we have:
>
> X(z) = 2/3/(1 - z^-1) - 2/3/(1 - 0.5z^-1)
>
> Now, we can use the formula for the inverse z-transform of a geometric series to find the inverse z-transform of each term:
>
> x_1[n] = (2/3)(z^n)
>
> x_2[n] = (-2/3)(0.5^n)
>
> Therefore, the overall inverse z-transform of X(z) is the sum of these two terms:
>
> x[n] = x_1[n] + x_2[n] = (2/3)(z^n) - (2/3)(0.5^n)
>
> The ROC of this sequence is |z| > 0.5, since that is the intersection of the ROCs of the two individual terms.