What is a simple form of this equation?

[mtkee2003]

simplest form

hi
i want a simple form for thir relation:

f(x)=u(x).u(x-n) where 'x' is variable and 'n' is an arbitrary constant.

i know that for:

n<0: if 0<k<infinity then f(x)=1 (and otherwise 0)

n>0: if n<k<infinity then f(x)=1 (and otherwise 0)
regards.

 

[LouisSheffield]

simplest form

Please clarify as to how "k" comes into the picture.