L'>M Pr 1=1 (3-48) P2 (3-49) P`=f(T),P=f2(7) P=Yx,P+r2x,P (3-50) P P1+P2 P-P.< p2 P,=PRix, p2=PSr2x2 Ps(-r x1) 则x1≈1,x2≈1,即 Ps x E P Yix=yixI (-x1)=y(-x2) (3-56) P=Pyx+Psri (-xI (3-57) = Y3 Pi P=Y,,Ps+y, P2+r,x, P3L W ( )s W s x  x 1 2 s 2 1 s 1 12 = =    P P （3-48） 12 =1 s 2 s 1 2 1 P P =   (3-49) P f (T ) P f (T ) = 1 = 2 s 2 s 1 , s s 1 1 1 2 2P2 P =  x P +  x (3-50) s s P = p1 + p2  P1  P2 (3-51) P1 − p1  p2 s (3-52) 2 2 2 2 1 1 1 1 1 p P x p P x 2   s 2 s = 1 , = ( ) 1 1 2 2 2 2 1 1 1 1  − P x P x   s 2 s 1 (3-53) 1 2 2 1 1 2 2 1 则x1  1，x  1，即    1 2 2 2 = •  x x P P E 1 s 2 s 1 (3-54) 1 2 2 1 1 1 1 1  x =  x (3-55) ( ) ( ) 2 1 x - x 2 1 2 1 1 2 1 1  − =  (3-56) ( ) 1 2 1 1 1 1 P P 1 x P 1 x 1 = 1  +  − s 2 s (3-57) 12 =13 = 23 =1 s s 1 1 3 3 P P =   (3-58) s s 3 2 2 3 P P =   (3-59) s s s 1 1 1 2 2 2 3 3P3 P =  x P +  x P +  x (3-60)