已知数列An的前N项和为Sn,且An=1,A(n+1)=1/3Sn,求a2,a3,a4的值及数列An的通项公式_数学解答

已知数列An的前N项和为Sn,且An=1,A(n+1)=1/3Sn,求a2,a3,a4的值及数列An的通项公式

人气：386 ℃　时间：2019-08-18 19:33:53

解答

a(2) = s(1)/3 = a(1)/3 = 1/3.a(3) = s(2)/3 = [a(1) + a(2)]/3 = [1 + 1/3]/3 = 4/9a(4) = s(3)/3 = [a(1) + a(2) + a(3)]/3 = [1 + 1/3 + 4/9]/3 = 16/27.a(n+1) = s(n)/3,a(n) = s(n-1)/3,a(n+1) - a(n) = [s(n)...