The problem asks us to form a quadratic expression based on the diagram. The diagram shows a right-angled triangle with sides labeled $p$, $q$, and $r$, where $r$ is the hypotenuse.

1. Problem Description

The problem asks us to form a quadratic expression based on the diagram. The diagram shows a right-angled triangle with sides labeled $p$, $q$, and $r$, where $r$ is the hypotenuse.

2. Solution Steps

Since the triangle is right-angled, we can apply the Pythagorean theorem:

$p^2 + q^2 = r^2$

We want to express this as a quadratic expression. The general form of a quadratic expression is $ax^2 + bx + c = 0$.

Rearranging the Pythagorean theorem, we get:

$r^2 - p^2 - q^2 = 0$

3. Final Answer

$r^2 - p^2 - q^2 = 0$