(1) a=2时b1=b 公比=2Sn=b1*(2^n-1)/(2-1)=b(2^n-1)Tn=b[∑2^n-∑1]=b[2*(2^n-1)/(2-1)-n]=b[2^(n+1)-n-2]cn=Tn-λSn=b*[2^(n+1)-n-2-λ*2^n+λ]=b*[(2-λ)*2^n+λ-n-2]若{cn}成等差数列c1=b*[(2-λ)*2+λ-2-1]=b*...