The problem defines a function $f(x, y) = \frac{x^2 - y^2}{xy}$. There are further expressions related to the function $f(x,y)$, but they are incomplete. We are asked to evaluate or understand $f(x, y)$.

1. Problem Description

The problem defines a function $f(x, y) = \frac{x^2 - y^2}{xy}$. There are further expressions related to the function $f(x,y)$, but they are incomplete. We are asked to evaluate or understand $f(x, y)$.

2. Solution Steps

We are given the function

$f(x, y) = \frac{x^2 - y^2}{xy}$

We can rewrite this as

$f(x, y) = \frac{x^2}{xy} - \frac{y^2}{xy}$

$f(x, y) = \frac{x}{y} - \frac{y}{x}$

If we are given $

2. f(x, y) = (4x - ...)$ or $

4. f(x, y) = e^x cos(...)$, then we could equate those to $\frac{x^2 - y^2}{xy}$ to find relationship between $x$ and $y$.

However the question is incomplete to proceed to next step.

3. Final Answer

$f(x, y) = \frac{x^2 - y^2}{xy} = \frac{x}{y} - \frac{y}{x}$