例4求 lim aon+a1mm+…+ans b≠0 n→0 bn"+bn”+…+b 小结:当a0≠0,b0≠0,m和n为非负整数时有 0,当n= lim on+an-1 +…+am=0,当n>m, n)∞bnn+b,nn-1+…+b ∞,当n<m小结: 当a0 0,b0 0,m和n为非负整数时有 = = + + + + + + − − → , , 0, , , , lim 0 0 1 0 1 1 0 1 n m n m n m b a b n b n b a n a n a n n n m m m n 当 当 当 例4 求 lim , 0 0 0 1 0 1 1 0 1 + + + + + + − − → a b b n b n b a n a n a n n n m m m n