By means of Nopital's rule may determine k, that is ki=lim (S-p;)N(s) =lin(s-Pi)N()+N(s)=im D(s)D(pi) N(s) N(Pi) s→Pi D(S) D'(S) s→ i=1,2, f(t)=[F(s)=(k,ePit+k2 ePat+.+knep,n )u(t) 4s+5 :F()=-2 2 s2+5s+6s+2s+3 4s+5 4s+5 K -3k 7 2s+5s 2 2s+5J=-3 ∴f()=(-3e-+7e)u(t)By means of Nopital' s rule may determine k, that is i , ,...n D'( p ) N( p ) D (s ) N(s) lim D'(s ) (s p )N'(s) N(s ) lim D(s ) (s p )N(s) k lim i i ' s p i s p i s p i i i i = 1 2 = = − + = − = → → → f (t ) L F(s) ( k e k e k e )u(t ) p t n p t p t n  = = + + + −1 1 1 2 2  5 6 2 3 4 5 : ( ) 1 2 2 + + + = + + + = s k s k s s s If F s 3 2 5 2 4 5 1 = − + = − + = s s s k 7 2 5 3 4 5 2 = + = − + = s s s k ( ) ( 3 7 ) ( ) 2 3 f t e e u t − t − t  = − +