Question

已知数列{An}是无穷等比数列,且公比q满足0

Answer 1

Sn=a1(1-q^n)/(1-q)

LimSn=a1/(1-q)

An=k(LimSn-Sn)=k*a1*q^n/(1-q)

An=a1*q^(n-1)

k=q^(n-1) * (1-q) / q^n = (1-q)/q = 1/q -1

-1