M=ga P=4a 2.34567 B 235 实际→。实下 4-4 q 2如3 q 2 MA4=-·9=qa·a=2° 3 2 5-5=+ga M. 5-5% -6=+ga M 16-6 ga 77=+a Mn.7=0 7Q4−4 = qa qa qa 2 3 2 1 − − = − M4−4 = 2 2 2 1 2 3 − qa  qa − qa  a = − qa Q5−5 = + qa M5−5 = 2 − qa Q6−6 = + qa M6−6 = 2 2 1 − qa Q7−7 = + qa M7−7 = 0