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Two parabolas have the same focus. If th...

Two parabolas have the same focus. If their directrices are the x- and the y-axis, respectively, then the slope of their common chord is `+-1` (b) `4/3` (c) `3/4` (d) none of these

A

-1

B

`-1//2`

C

`-sqrt(3)//2`

D

none of these

Text Solution

Verified by Experts

The correct Answer is:
A
(1) Let the focus be F. The parabola are open-down and open-right, respectively.
Let the parabolas intersect at point P and Q. From P, perpendiculars are drawn on the x-and the y-axis at A and B, respectively, Then,
PA=PF=PB
So, P lies on the line =-x.
Similarly, Q lies on the y=-x. Therefore, Slope of PQ =-1
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