1£®ÒÑ֪ȫ¼¯ £¬ £¬Ôò £¨ ¡¡£©
£¨A£© £¨B£© £¨C£© £¨D£©
2£®º¯Êý µÄ¶¨ÒåÓòΪ£¨ £©
£¨A£© £¨B£©(1£¬+∞) £¨C£©[1£¬2) £¨D£©[1£¬+∞)
3£®Éè ÊǶ¨ÒåÔÚRÉϵÄÆ溯Êý£¬µ± ʱ£¬ £¬Ôò £¨ £©
£¨A£©1 £¨B£©£­1 £¨C£©3¡¡¡¡¡¡¡¡¡¡£¨D£©£­3
4£®Ó뺯Êý ±íʾͬһ¸öº¯ÊýµÄÊÇ£¨ ¡¡£©
£¨A£© £¨B£© £¨ £¬ÇÒ £©
£¨C£© £¨D£© £¨ £¬ÇÒ £©