0 =0 g100+a1-pi q20+q101+a2-P2=0 (1.103) q30+q21+y102+a3-p3=0 gMaN-M+ 9M-1aN-M+1+.+aN-PN ane gMaN-M+1+9M-1aN-M2+.+gIaN +aN+1=0 ④MN-M+2+M=1N-M+3+…+91N+1+aN+2=0 1.104 gMaN +9M-1aN+1+.+glaN+M-1+aN+M=0