History of Hindu Mathematics: A Source Book v2.c17.s8.115

v2.c17.s8.115

We need not add further instances to prove that Mahâvîra recognised both the roots of a quadratic equation.³ There are, however, a few problems in which he has taken into consideration only one of the roots.⁴ For instance, take the equation on page 66, $¼x + 2√x + 15 = x,$ or ¾x - 2√x = 15. Therefore √x = 4/3 ± √((4/3)² + 4.15/3), or √x = (4/3 ± 14/3) = 6 or -10/3. ∴ x = 36. The root can not be negative, hence the negative value of the radical is neglected in the rule.