若a,b,c为等差数列,b,c,d为等比数列,1/c,1/d,1/e为等差数列,则a,c,e成?
问题描述：
若a,b,c为等差数列,b,c,d为等比数列,1/c,1/d,1/e为等差数列,则a,c,e成?
答
2b = a+c.
c^2 = bd = (a+c)d/2,2/d = (a+c)/c^2
2/d = 1/c + 1/e = (a+c)/c^2 = a/c^2 + 1/c,
1/e = a/c^2,
c^2 = ae
a,c,e 成等比数列.