P1(N1,0),P2(0,N2),P3 N1(1-a1)N2(1-2 ),P4(0,0) 2x r1( A 2. 1 2 NI r2(1 因此,P=-(fx+g,)|,q=deA|p,i=1,2,3,4 N1(1-σ1) 对P,A N,(I r2G2N2(1-a2) f(1-a1)(1-2)), (0,0). 1 (1 ) , 1 (1 ) ( ,0), (0, ), ( 4 1 2 2 2 1 2 1 1 1 1 2 2 3 P N N P N P N P       − − − − , ( )| , det A | , 1,2,3,4. ) 2 (1 ) 2 (1 A 1 2 2 2 1 1 2 2 1 2 2 2 2 1 1 1 2 2 1 1 1 1 = − + = =             − − − − − − = p f g q i N x N x r N x r N x r N x N x r Pi Pi 因 此 x x                 − − − − − − − − − − = 1 2 2 2 1 1 2 2 2 2 2 2 1 2 1 1 1 1 1 2 1 1 3 1 ( 1) (1 ) (1 ) (1 ) (1 ) 1 ( 1) ,               r N r N N r r N 对P A 1 2 1 2 1 2 1 (1 )(1 )     − − − = r r q