.
If you think 1 - 2 minutes, you will get that
BLANK = f(5).
In other words, you need substitute the value x= 5 into the function f(x), defined in the post,
and calculate the value f(5).
It is SO EASY, that you can do it on your own, without my help.
Do not forget to post your "THANKS" to me for my explanations.