f1(x)=(x-1)/(x+1)=1-2/(x+1),f2(x)=[(x-1)/(x+1)-1]/[(x-1)/((x+1)+1]=(-2/x+1)/[(2x/(x+1)]=-1/xf3(x)=(-1/x-1)/(-1/x+1)=(1+x)/(1-x),f4(x)=[(1+x)/(1-x)-1]/[(1+x)/(1-x)+1]=x,f5(x)=(x-1)/(x+1)=f2(x),所以该函数周期为4,所以f2008(x)=f(4+4*501)(x)=f4(x)=x,所以就是判断x=x2-2x+2是否有实数解,它的解是x=1,x=2,所以选D... |