9?????20??,?????????????????“????????”??????“????????????”???????????????,??,??

?,???“?”,??????????????,?????20???????????????????????19??????????,??80??,??20???

(? ??? ???? ?????? ???? ?????????????)

???:??????

??“??????????”????

?? ???????? ???????“?????”??

????:1???????????:????sn

2??????

3????????

4???????????????

5?????

9?????20??,?????????????????“????????”??????“????????????”???????????????,??,??

?,???“?”,??????????????,?????20???????????????????????19??????????,??80??,??20???

(? ??? ???? ?????? ???? ?????????????)

???:??????