Quantcast

A community for students.

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

lissafi

  • 2 years ago

show that the two circlex^2+y^2-4x-2y-11=0 and x^2+y^2+20x-12y+72=0 do not intersect.Hint;find the distance between their centers

  • This Question is Closed
  1. wio
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Use completing the square to get them both in the form of :\[ (x-h)^2+(y-k)^2=r^2 \]

  2. wio
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    For example: \[ x^2-4x = (x-2)^2-4 \]

  3. lissafi
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i still cant work it wio

  4. Yahoo!
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 2

    General equation: x^2 + y^2 +2gx + 2hy + c=0 Centre ( -g,-f)

  5. Yahoo!
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 2

    x^2+y^2-4x-2y-11=0 Centre (2,1)

  6. Yahoo!
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 2

    x^2+y^2+20x-12y+72=0 Centre (-10,6)

  7. Yahoo!
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 2

    Hope this will help u..

  8. wio
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Still gotta find radius though. @Yahoo!

  9. Yahoo!
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 2

    \[r=\sqrt{g^2+f^2-c}\]

  10. wio
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    You really learn that in class?

  11. lissafi
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    @yahoo how do u get the center x^2+y^2+20x-12y+72=0 Centre (-10,6)?

  12. Yahoo!
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 2

    Compare it with the General equation..

  13. Yahoo!
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 2

    x^2 + y^2 + 2gx + 2fy + c=0 C ( -g,-f) so Here x^2+y^2+20x-12y+72=0 2g = 20 g = 10 2f = -12 f = -6 Since the Centre is -g,-f C ( -10 , - (-6) ) C ( -10 , 6)

  14. wio
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    @lissafi Do you know how to complete the square?

  15. lissafi
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    not on this

  16. wio
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Just ignore the \(y\) terms and try to complete the square for (x\), then ignore the \(x\) terms and complete the square for \(y\)

  17. lissafi
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    wio is that what yahoo did?cos i am lost on this method

  18. wio
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    I dunno what Yahoo! did...

  19. wio
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    \[ x^2+y^2-4x-2y-11=0 \]Okay so we just ignore the \(y\) terms... \[ x^2-4x-11=0 \]How do you complete the square here?

  20. lissafi
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    wio i dont know much on completing the square

  21. wio
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Look it up...

  22. Yahoo!
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 2

    x^2+y^2-4x-2y-11=0 x^2-4x + y^2 -2y = 11 x^2 - 4x + 4 + y^2 - 2y + 1 = 11 + 4 + 1 (x-2)^2 + (y-1)^2 = 16 (x-2)^2 + (y-1)^2 = 4^2 now it is a circle with centre (2,1) and radius 4

  23. Yahoo!
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 2

    @lissafi u got it..now

  24. lissafi
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yap,and for x^2+y^2+20x-12y+72=0?

  25. Yahoo!
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 2

    Try it out...

  26. lissafi
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i lost in (x-2)^2 + (y-1)^2 = 16

  27. lissafi
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i know you add +4+1 on both side

  28. Yahoo!
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 2

    Since we added 4 and 1 on LHS we have to do in RHS tooooo

  29. lissafi
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i know you can find x to subtitute to get y and have the points,but i dont know this method

  30. sirm3d
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    in \[x^2+y^2+20x-12y+72=0\] what term must be added to \[x^2+20x\] to get a perfect square trinomial that can be written in the form \[(x+\_\_)^2\]

  31. Not the answer you are looking for?
    Search for more explanations.

    • Attachments:

Ask your own question

Sign Up
Find more explanations on OpenStudy
Privacy Policy

Your question is ready. Sign up for free to start getting answers.

spraguer (Moderator)
5 → View Detailed Profile

is replying to Can someone tell me what button the professor is hitting...

23

  • Teamwork 19 Teammate
  • Problem Solving 19 Hero
  • You have blocked this person.
  • ✔ You're a fan Checking fan status...

Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.

This is the testimonial you wrote.
You haven't written a testimonial for Owlfred.