Question

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

Answer 1

f(1+2)=f(3)=1/f(1)=-1/5

f(3+2)=f(5)=1/f(3)=-5

f(f(5))=f(-5)

f(x)=1/f(x+2)

f(-5)=1/f(-5+2)=1/f(-3)

f(-3)=1/f(-3+2)=1/f(-1)

f(-1)=1/f(-1+2)=1/f(1)=-1/5

f(-3)=-5

f(-5)=-1/5