バースカラ2世
The first general method for solving the Pell equation (for all "N") was given by Bhāskara II in 1150, extending the methods of Brahmagupta. Called the chakravala (cyclic) method, it starts by choosing two relatively prime integers formula_19 and formula_20, then composing the triple formula_21 (that is, one which satisfies formula_22) with the trivial triple formula_23 to get the triple formula_24, which can be scaled down to