对前面等式的说明 ∩E (=∩E >a 1= n=1 f≥a-1 [n+∞)=∩(a-n,+∞)( nla + 1/n a a a+1/r (a+∞)=[a+n,+∞)(=(a+1,+∞) n=1 ∪E (=∪E a+ >a+对前面等式的说明 ( ) [ ] 1 [ ] 1 [ ] 1 1 n n f a n f a n E f a E E  −  =  −  =  =  =  [ , ) ( , ) ( [ , ) ) 1 1 1 1 + =  − + =  − +  =  = n n n n a a a ( [ a-1/n a ( ) [ ] 1 [ ] 1 [ ] 1 1 n n f a n f a n E f a E E  +  =  +  =  =  =  ( , ) [ , ) ( ( , ) ) 1 1 1 1 + =  + + =  + +  =  = n n n n a a a ( [ a a+1/n