對(duì)數(shù)有意義,ab>0 a,b,ab成等比數(shù)列,設(shè)公比為q (q≠0) a=ab/q²>0,因此b>0
a>0 b>0
a,b,a+b成等差數(shù)列,則2b=a+a+b
b=2a
a,b,ab成等比數(shù)列,則
b²=a(ab)=a²b b=a²
2a=a² a(a-2)=0 a=0(舍去)或a=2
b=2a=4 ab=8
0