The problem defines a function $f(x, y)$ as $f(x, y) = \frac{x^2}{xy - y^2}$.

1. Problem Description

The problem defines a function $f(x, y)$ as $f(x, y) = \frac{x^2}{xy - y^2}$.

2. Solution Steps

The problem presents a function $f(x, y)$ defined as:

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

The function is already given. No further steps are needed to simplify it.

3. Final Answer

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