Question
Question: variable curves C<sub>1</sub> : y<sup>2</sup> = 4a(x – b<sub>1</sub>) and C<sub>2</sub>: x<sup>2</su...
variable curves C1 : y2 = 4a(x – b1) and C2: x2 = 4a
(y – b2) where 'a' is a given positive real number and b1 and b2 are variables, touch each other. Locus of the point of contact is
A
xy = a2
B
xy = 2a2
C
xy = 4a2
D
None
Answer
xy = 4a2
Explanation
Solution
Let P(x, y) be the point of contact. Slope of the curves at the point of contact are and
. Thus y2a=2ax
⇒ xy = 4a2.