Parabolics question Watch

2strong
Badges: 1
Rep:
?
#1
Report Thread starter 10 years ago
#1
1). The rectangular hyperbola H has equation xy = c^2

The points P (cp, c/p) and Q (cq, c/q) lie on H

a) Show that the gradient of the chord PQ is -1 / pq

Ive done that, simple y diff/x diff standard!

b) The point R (3c, c/3) also lies on H and PR is perpendicular to QR. Show that this implies that the gradient of PQ is 9.

I dont get b). How do you show that?

ANY HELP?
0
quote
reply
Swayum
Badges: 18
Rep:
?
#2
Report 10 years ago
#2
You've already shown the gradient of the chord PQ is

-1/pq. The question is now asking you to show that this is going to be 9. This implies you're trying to show that pq = -1/9 (because -1/(-1/9) = 9).

Can you show that?

Hint

Spoiler:
Show
If PR is perpendicular to QR, then their gradients when multiplied = -1.
0
quote
reply
X

Reply to thread

Attached files
Write a reply...
Reply
new posts
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

University open days

  • University of Lincoln
    Brayford Campus Undergraduate
    Wed, 12 Dec '18
  • Bournemouth University
    Midwifery Open Day at Portsmouth Campus Undergraduate
    Wed, 12 Dec '18
  • Buckinghamshire New University
    All undergraduate Undergraduate
    Wed, 12 Dec '18

Do you like exams?

Yes (166)
18.57%
No (543)
60.74%
Not really bothered about them (185)
20.69%

Watched Threads

View All