(1)当A<0时 x(x)=Aev-Ax+Be -Ax X(0)=A.1+B·1=0 X(L)=Aev-xL+Be-AL=o 从而 X(x)≡00.8 1 0.6 0.4 0.2 0 x t 0 0.5 1 1.5 2 −1 −0.5 0 0.5 1 n 9 (1) 当   0 时 ( ) x x X x Ae Be − − − = + ( ) 0 (0) 1 1 0 = + = =  +  = − L − − L X L Ae Be X A B   从而 X x( ) 0 