第2个回答 2013-03-31
an + S(n-1) = Sn = 2an+n
an = S(n-1) - n
a1 = -1, Sn = -1
a2 = S1 - 2 = -3, S2 = - 4
a3 = S2 - 3 = -7, S3 = -11
a4 = S3 - 4 = -15, S4 = -26
a5 = S4 - 5 = -31, S5 = -57
a6 = S5 - 6 = -63
f(3/2-x) = f(x)
f(x) = f(3/2-x) = -f(x - 3/2) = - f(3-x) = f(x -3)
所以同期为3