How to generate bigger value for Y=X/N when X becomes smaller?

Question

I am not specialist in Math, I just want to know if there is any operation(or formulation) that can be used to return bigger value for Y when X becomes smaller? I have tried to use Square root For example:

Square root and exponential operations returns smaller value for Y when X value become smaller and this is not what I want.

   N = 200
   Y = X/N

Using Square root

Y = sqrt(10/200) = 0.2236
Y = sqrt(5/200) = 0.15811

Same with exponential operation

Y = exp(10/200) = 1.0513    
Y = exp(5/200) = 1.0253

I have this formulation:

Y = X/N   ;   where ***N*** is constant
Z = 2-2*(Y)^5

Here the value of X changes over time. When X becomes smaller, the value of Y should became bigger. Then, Z becomes smaller. The value of Z must be positive in interval [0,2].

Y value must be positive.

Which operation can be used to do this?