History of Hindu Mathematics: A Source Book v2.c17.s14.32

v2.c17.s14.32

$13x²-13=y².$ One solution of it is given by the author as x=1, y=0; so that here the lesser root is greater than the greater root. The same is the case in the solution x=2, y=1 of his example (*BBi*, p. 43) $-5x²+21=y².$ Brahmagupta gives the example (*BrSpSi*, xviii. 77) $3x²-800=y²,$ which has a solution (x=20, y=20) where the two roots are equal.