设等比数列为{an}，公比为q，由题意可得 a1a2a3=3，且 an-2an-1an=9，两式相乘可得 a1an =3．再由所有项的积为a1•a1q•a1q2 …a1qn-1=729=36 ①，倒序可得 a1qn-1…a1q2•a1q•a1=36 ②，把①②对应项相乘可得...