### Introduction

Fermat's Last Theorem states the following:

For \(n=2\), the triple \(x=3, y=4, z=5\) is a solution; another one is \(x=8, y=15, z=17\). But, for instance, for \(n=4\), one can say that, for any natural numbers \(x, y, z\), we have \(x^{4}+y^{4}\neq z^{4}\).

Taking, for each natural \(n\), the surface defined by the points in space
whose coordinates satisfy the identity \(x^{n}+y^{n}=z^{n}\), one may give a
geometrical interpretation of the statement of Fermat's Last Theorem. The
applet in this page illustrates this interpretation. For more information about
the Theorem, consult the page "Fermat's Theorem".

A natural question associated with Fermat result is about the number of (integer)
solutions corresponding to a given \(z\), when \(n=2\), or, more generally,
about the number of integer solutions of the equation (in \(x\), \(y\)) \(x^{2}+y^{2}=m\),
for each natural number \(m\). These questions are related with several other
interesting problems, some of them solved by Gauss himself. Meanwhile, you may
play with the applet below.

For more information click here.

This *applet* uses **Javaview**

If you have difficulty seeing the applet, click here.

(*) This work was carried out under a grant by FCT - Fundação para a Ciência e a Tecnologia.