對(duì)于等差數(shù)列來說；a(n+1)=（a1+a(2n+1)）/2,
對(duì)于等比數(shù)列來說：b²(n+1)= b1•b(2n+1),
由基本不等式得:（a1+a(2n+1)）/2≥√(a1•a(2n+1))
=√(b1•b(2n+1))=√(b²(n+1))=| b(n+1)|≥b(n+1),
即：a(n+1) ≥b(n+1).