例: r(n=a u(n X(2)=∑a=m=(a)y 0 lim an+1=az z n→>00 laz lim vaz=az=p →005 例： x ( n ) a u ( n ) n =  = − = − = = 0 1 0 ( ) ( ) n n n n n X z a z az = =  + − →  1 1 lim az aa nn n a z a z a z = = =  − − →  1 1 lim az az n n n