Question

如题.已知等比数列{an}的前n项和Sn=a^n+K,求an的通项公式是——需过程.

Answer 1

a1=s1=a+k

Sn=(a+k)(1-q^n)/(1-q)=a^n+k

所以(a+k)/(q-1)=1

(a+k)/(1-q)=k

q=a,k=-1,an=(a-1)a^(n-1)