Question

简单的数列题

数列An的前项和为Sn=1/2n^+1/2n,n属于自然数,求通向公式

Answer 1

a1=1/2
an=S(n+1)-Sn=-1/2^n+1/(2n+2)-1/2n (n>1)

Answer 2

a1=S1;
an=Sn-S(n-1),n>=2;