Question

If 2 is a root of the equation x² + bx + 12 = 0 and the equation x² + bx + q = 0 has equal roots, then q = 

A. 8 

B. – 8 

C. 16 

D. – 16

Answer 1

2 is the root of given equation x² + bx + 12 = 0 

So 2² + 2b + 12 = 0 

16 + 2b = 0 

b = – 8…………..1 

Now, d = b² – 4ac = 0 of second equation is 

d = b² – 4 (1) (q) = 0 here a = 1, b = – 8 (from 1) and c = q 

(– 8)² – 4q = 0 

64 – 4q = 0 

q = 16 

Hence value of q is 16.