Ex.3.3:Sum of two exponential sequences 24+立(4 xIn]=a"uln] 2+ X(②1-az ROCa 2z 12 1 1-+ ROC: 1919 Ex.3.3: Sum of two exponential sequences 1 2 ROC: z  1 3 and z  : 1 2  ROC z  ( ) ( ) 0 1 1 0 1 1 2 3 n n n n z z   − − = = = + −   1 1 1 1 2 z − = − 1 1 1 1 3 z − + + ( ) ( )( ) 1 1 1 2 12 1 1 1 1 2 3 z z z z − − − = − +     n x n a u n = ROC z a :  ( ) 1 1 1 X z az = − − ( ) ( )   ( )   1 1 2 3 n n n n n n X z u n z u n z   − − =− =− = + −  