Question

If a, b and c are real and satisfy the equation 4a² + 9b² + 12ab – 9c² + 0, then ax + by + c = 0 represents two families of concurrent lines. The distance between their points of concurrence is

(A)   1

(B)   3√3

(C)   2/3√13

(D)   2√13

Answer 1

Correct option  (C)   2/3√13

Explanation :

From the given relation we have

which implies that ax + by + c = 0 passes through

(2/3,1) or(-2/3, -1)

 whose distance between them

2√13/3