JEE Main202330 Jan 2023Evening ShiftMathematicsParabolaActual
The parabolas : a x 2 + 2 b x + c y = 0 and d 2 + 2 e x + f y = 0 intersect on the line y = 1 . If a , b , c , d , e , f are positive real numbers and a , b , c are in G . P . , then
Options
- Ad , e , f are in A.P.
- Bd a , e b , f c are in G.P.
- Cd a , e b , f c are in A.P.
- Dd , e , f are in G.P.
Correct answer
C. d a , e b , f c are in A.P.
Step-by-step solution
Given, a x 2 + 2 b x + c y = 0 and d 2 + 2 e x + f y = 0 intersect on the line y = 1 , And a , b , c are in G.P. So, b 2 = a c Now putting the value of b in a x 2 + 2 b x + c y = 0 and taking y = 1 we get, a x 2 + 2 b x + c = 0 ⇒ ax 2 + 2 ac x + c = 0   ∵ b 2 = ac ⇒ ( x a + c ) 2 = 0 ⇒ x = - c a and x 2 = c a   . . . . . . . 1 Now, putting the value of x   &   x 2 in d x 2 + 2 e x + f y = 0 and taking y = 1 we get, ⇒ d c a + 2 e - c a + f = 0 ⇒ d c a + f =