Example 3.5: Two-sided exponential sequence 网=(--小 xn=aun] Solution:Right-sided Left-sided X2片1-az 女时 ROC:>a x[n-4-n-刂 形寸好 X(}Iazt ROC:a X(2F 2-12 1 22可c 2323 Example 3.5: Two-sided exponential sequence   ( )   ( )   1 1 1 3 2 n n x n u n u n = − − − − ， ( )   1 1 1 , 3 1 1 3 1 3 n Z u n z z − −  +  ( )   1 1 1 1 , 2 1 1 2 1 2 n Z u n z z − − − − −   ( ) 1 1 1 X z az = − − ROC: z a     1 n x n a u n =− − − Solution: 1 1 3 : 2 ROC  z Right-sided Left-sided ( ) ( )( ) 1 1 1 2 12 , 1 1 1 1 3 2 z z z z − − − = + − ( ) 1 1 1 1 1 1 1 1 3 2 X z z z − − = + + −     n x n a u n = ROC z a :  ( ) 1 1 1 X z az = − −