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问题: 函数

设函数y=f(x)满足f(1)=4,f(2)=1,f(3)= 3, f(4)=5, f(5)=2,数列{xn}满足x0=5且对任意自然数均有x(n+1)=f(x),则f(x(2008))=? (2008下标)

解答:

对任意的自然数n,都有 x(n+1) = f(xn)
 且 x0 = 5
所以 x1 = f(x0) = f(5) = 2
   x2 = f(x1) = f(2) = 1
   x3 = f(x2) = f(1) = 4
   x4 = f(x3) = f(4) = 5 = x0
 故 x5 = ................ = x1
   x6 = ................ = x2
   x7 = ................ = x3
   x8 = ................ = x4
 .............................
由周期性,可得 x2008 = x0 = 5
故 f(x2008) = f(5) = 2