已知数列{an}是等比数列，在数列{a(n+1)an};{a(n+1)+an};

a(n+2)a(n+1)=q*a(n+1)*q*an
=q^2*a(n+1)an
{a(n+1)an}是等比数列

a(n+2)+a（n+1）=q*a(n+1)+q*an
=q[a(n+1)+an]
{a(n+1)+an}是等比数列

{ananan}看不懂

{nan}不是等比数列
（n+1)a(n+1)/nan=(n+1)/n*q，与n有关，所以不是等比数列

数列{an}是等比数列,设an/a(n-1)=r
数列{a(n+1)an}
[a(n+1)an]/[ana(n-1)]=[a(n+1)/an][an/a(n-1)]=r^2 仍是等比数列
{a(n+1)+an}
[a(n+1)+an]/[an+a(n-1)]=r[an+a(n-1)]/[an+a(n-1)]=r仍是等比数列
{ananan}
(ananan)/[a(n-1)a(n-1)a(n-1)]=r^3仍是等比数列
{nan}
nan/[(n-1)a(n-1)]=nr/(n-1)不是固定比值，所以不是等比数列