询问几道数学题啊
1.在数列{an}中,已知a1=5,a2=2,an=2an-1+3an-2(n≥2)
证明:(1){an+an-1}(n≥2)成等比数列
(2){an-3an-1}(n≥2)成等比数列
2.已知等比数列{an}各项为正,且a1,1/2a3,a2成等差数列,求a3+a4/a4+a5