函数f(x)对于任意实数x满足条件f(x+2)=1/f(x).若f(1)=-5,则f[f(5)]

∵f(x+2)=1/f(x)
∴f(5)=f(3+2)=1/f(3)=1/f(1+2)=1/[1/f(1)]=f(1)=-5
∵f(x+2)=1/f(x)
∴f(x)=1/f(x+2)
∴f(-5)
=1/f(-5+2)
=1/f(-3)
=1/[1/f(-3+2)]
=f(-1)
=1/f(-1+2)
=1/f(1)
=-1/5
∴f[f(5)]=-1/5