证明:1)∵ {an}是严格单调减且收敛于0
∴a1>a2.>an>a(n+1)>0
A(n+1) -An=[a1+a2+.+a(n+1)]/(n+1) - [a1+a2+.+an]/n
=a(n+1)/(n+1)+[1/(n+1)-1/n][a1+a2+.+an]
证明:1)∵ {an}是严格单调减且收敛于0
∴a1>a2.>an>a(n+1)>0
A(n+1) -An=[a1+a2+.+a(n+1)]/(n+1) - [a1+a2+.+an]/n
=a(n+1)/(n+1)+[1/(n+1)-1/n][a1+a2+.+an]