Subordination is a term used when designers set viewing preferences in a order.

Subordination is a term used when designers set viewing preferences in a importance order.

Explanation:

The subordination art technique is the technique of toning down non-essential elements in order to bring attention to the focal point.

So

Subordination is a term used when designers set viewing preferences in a importance order.

to answer your question:

f(x)= a^x.  if x=0, f(x)=1  if x=1, f(x)=a  if x=1, f(x)=a^a