How do I describe this relation?

Question

I have an equation and I would like to express in words the relationship between a and b, where

$$a = \frac {1}{x - b}$$

in a similar (physics-y) vein to "a Is directly/inversely proportional ... to b"...

Is there an accurate way to do this? (x is constant)

Sorry if this belongs in physics

Answer 1

Thank you to ajotatxe for commenting the answer I wanted.

"$a$ is inversely proportional to the difference between $x$ and $b$"