//Returns Tuple(x,y) for x^2 - Dy^2 = 1;
public static Tuple <BigInteger, BigInteger> SolvePellEquation(int D)
{
BigInteger x, y;
List <int> liSCF = Numbers.SqrtContinuedFraction(D);
int r = Math.Max(liSCF.Count - 2, 1);
BigFraction bf;
if (r % 2 == 0)
{
bf = BigFraction.SqrtConvergent(D, 2 * r + 1);
}
else
{
bf = BigFraction.SqrtConvergent(D, r);
}
bf.Reduce();
x = bf.Numerator;
y = bf.Denominator;
return(new Tuple <BigInteger, BigInteger>(x, y));
}
