?? ??6.4???????????27? ????
????:1???????:??????????
2?????vx
3??????????
4??????
5???????????
?1?21????? ?????,21???????????????????17??,?6.4???????????????????????,????27?????,??????
???????????????,?????????????????11??,???????????55??,???????5??
?????????????,?????,?????,?????,?????????????????,???????,?????????4????????????????????10???????????????
??????????????????????,????????????????10????,???????????????????????22???????????????????????,????????????????????????
?????????,???????????,??????????????????????????????21????????,????????,?,???????,???????????????????(??) ??????:?????