f

(
x
) =
|
x

6
|
7

x
, then
f
(

1)

Wow, why are you typing like this ?

f (x) =|x− 6|7−x, then f(−1)

the |x-6|7 makes little sense.
in algebra, a coefficient is usually written in front
e.g. 5x instead of x5

did you mean |x-6|^7 ?