a(n) = q^(n-1),
q=1时,s(n) = n. lim n↪∞ S(n+1)/Sn=lim n↪∞ (n+1)/n=1,满足题意。
q不为1时,s(n) = [q^n - 1]/(q-1),
|q|1时,lim n↪∞ 1/q^n=0.
lim n↪∞ S(n+1)/Sn=lim n↪∞ [q...
a(n) = q^(n-1),
q=1时,s(n) = n. lim n↪∞ S(n+1)/Sn=lim n↪∞ (n+1)/n=1,满足题意。
q不为1时,s(n) = [q^n - 1]/(q-1),
|q|1时,lim n↪∞ 1/q^n=0.
lim n↪∞ S(n+1)/Sn=lim n↪∞ [q...