Question

If one root of the equation x² + px + 12 = 0 is 4, while the equation x² + px + q = 0 has equal roots, then the value of q is
(a) 3 

(b) 12 

(c) 49/4 

(d) 4.

Answer 1

(c) : As x² + px + q = 0 has equal roots ∴ p² = 4q and one root of x² + px + 12 = 0 is 4.
∴ 16 + 4p + 12 = 0 ∴ p = –7
∴ p² = 4q => q =49/4