The improperly named Pell equation (Euler wrongly attributed it to him), which we have dealt with in previous weeks, was already studied in ancient times, both in India and Greece, especially the one with coefficient 2, that is, x² – 2y² = 1. Due to its relationship with the square root of 2, the first of the irrational numbers to be discovered (as a diagonal of a square with side 1), which both disturbed the Pythagoreans (to the point that it is said that they tried hide the discovery).
