• Congratulations to the Class of 2024 on your results!
    Let us know how you went here
    Got a question about your uni preferences? Ask us here

Conic Question Help (1 Viewer)

soyasauce

New Member
Joined
Sep 15, 2012
Messages
3
Gender
Male
HSC
2014
Can someone help me with this question? I know you can find the equation of the focal chord and do simultaneous equations with the hyperbola but this seems pretty tedious. Is there a quicker way to do this problem?
Thank you!
 

Attachments

ilikecake

New Member
Joined
Nov 19, 2013
Messages
5
Gender
Male
HSC
2014
If we have a look at the equation, we see that the eccentricity of this hyperbola is the square root of 1+9^2/3^2. i.e. eccentricity = 2.

If we then look at the focus of this hyperbola, we see that it is 2(sqrt3), which is also the x-coordinate of P. Therefore we know that since P is the extremity of a focal chord, and it lies on the same vertical line as the focus, then P is the end of the latus rectum.

By recalling the length of a latus rectum of a hyperbola as 2.(b^2/a^2), we clearly see that the length is 6 units.

By subtracting 6 from 2(sqrt3), we then know the x-coordinate of Q for answer.

Most of these conics questions should have an alternative solution if they give you a point on the conic not in parametric form, most of time it's just if you can see it or not :)
 

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top