Question

數(shù)列{a_n}共3n項(xiàng)，前n項(xiàng)和為S₁，中間n項(xiàng)和為S₂，最后n項(xiàng)和為S₃．

求證：(1)若{a_n}成等差數(shù)列，則S₁，S₂，S₃也成等差數(shù)列；

　　　(2)若{a_n}成等比數(shù)列，則S₁，S₂，S₃也成等比數(shù)列．

Answer 1

答案：