(1)R>2 Ae1+Ae l(0)=U→A1+A42=U du i(0+)=-C-(0+) 1 dt P →B1A1+P2A2=0 U PIt- Pie e P-P(1) 2 C L R  p t p t c u A e A e 1 2 = 1 + 2 0 1 2 0 uc (0 ) = U → A + A = U + 0 (0 ) (0 ) → 1 1 + 2 2 = = − + + P A P A dt du i C c        − − = − = 0 2 1 1 2 0 2 1 2 1 U P P P A U P P P A ( ) 1 2 2 1 2 1 0 P t P t c P e P e P P U u − − =