0《@-生1+24+2-+1 g4o-42 o=2+R)-e]       + − + + + + = i 1 ) P i 2 P i ( P 2 1 3 1 i 1 (0) P i Q        i  = ( Pi + Pi+2 )− Pi+1 2 1 Q (0) 2 ) i P i 2 ( P 2 1 (0) i Q − +  =