F(x) = 1/x ,f(f(f(f(f(f(x))))))=??

f(x) = 1/x ,f(f(f(f(f(f(x))))))=??

1 Answer
Jun 26, 2018

#f# is its own inverse, so an even number of them composed, six here, gets us back where we started:

#f(f(f(f(f(f(x)))))) = x#

Explanation:

One application of #f# gives the reciprocal:

#f(x) = 1/x#

Two gives us the reciprocal of the reciprocal, which is #x#

#f(f(x)) = f(1/x) = 1/(1/x) = x#

Three applications give us #1/x#:

#f(f(f(x)))=f(x) = 1/x#

We see four applications gives us #x#, five gives us #1/x#, etc. An even number gives us #x# and an odd number #1/x#.