Answer:
The given function
was replaced with
then the value of k is -3
that is k=-3.
Explanation:
The given function is
and when x=x+k then

Now to find the value of k:
Put x=x+k in the function f(x)
Now comparing equations (2) and (3) we get







Therefore k=-3
Therefore the given function
was replaced with
then the value of k is -3
that is k=-3.