Question

設(shè)數(shù)列{a_n}的前n項(xiàng)和為S_n，則下列說(shuō)法錯(cuò)誤的是________．

①若{a_n}是等差數(shù)列，則{3a_n+1－2a_n}是等差數(shù)列；

②若{a_n}是等差數(shù)列，則{|a_n|}是等差數(shù)列；

③若{a_n}是公比為q的等比數(shù)列，則{a_n+1－a_n}也是等比數(shù)列且公比為q；

④若{a_n}是公比為q的等比數(shù)列，則S_k，S_2k－S_k，S_3k－S_2k(k為常數(shù)且k∈N)也是等比數(shù)列且公比為q^k．

Answer 1

答案：②③