limb=b →0 n→0 liman=a, limb=b n→00 n→0 VE>0,3N(6)>0,当n>N时,有 a-al< b-b< An-4= a+i(b-b)< +1b.-bl n 88 <一十 lim A= A n→0a a, b b n n n n  lim = lim = → → ( ) a a, b b n n n n lim = lim = → →  2 2 0 0     −  −        a a , b b , N( ) , n N , n n 当 时 有  An − A = an − a + i( bn − b )  an − a + bn − b     + = 2 2 lim An A n  = →