∵a＝2? 3 ，∴a-1=1- 3 ∴ a2?1 a+1 ? a2?2a+1 a2?a ? 1 a = (a+1)(a?1) a+1 - |a?1| a(a?1) - 1 a =a-1- ?(a?1) a(a?1) - 1 a =a-1+ 1 a - 1 a =a-1=1- 3 ．
