Quantcast

Got Homework?

Connect with other students for help. It's a free community.

  • across
    MIT Grad Student
    Online now
  • laura*
    Helped 1,000 students
    Online now
  • Hero
    College Math Guru
    Online now

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

savvers Group Title

-4sqrt(x+9)=20 can anyone help?

  • one year ago
  • one year ago

  • This Question is Closed
  1. geoffb Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    \[-4 \sqrt{(x+9)} = 20\] Like this? At what part are you getting stuck?

    • one year ago
  2. savvers Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    well i get x=16 but when i try to see if its true i get -20=20

    • one year ago
  3. savvers Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    and yes like that

    • one year ago
  4. geoffb Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    Yeah, with that -4 outside the square root, I think it's undefined.

    • one year ago
  5. savvers Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    yeah your probably right. extraneous solution?

    • one year ago
  6. geoffb Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    If we defined \(y\) as \(\sqrt{(x+9)}\), we would get \(-4y = 20\), with \(y = -5\), and there is no way \(\sqrt{(x+9)} = -5\)

    • one year ago
  7. savvers Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    hmmm i dont know. but when we divide -4 we get \[\sqrt{x+9}=-5\]

    • one year ago
  8. geoffb Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    \(\large{\sqrt{-x} = i \sqrt{x}}\) right?

    • one year ago
  9. savvers Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    yeah

    • one year ago
  10. geoffb Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    Okay, can we use that somehow?

    • one year ago
  11. geoffb Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    Oh wait... We can square both sides, right?

    • one year ago
  12. savvers Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    hmmm yeah

    • one year ago
  13. savvers Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    and we get x+9=25 because -5x-5=25

    • one year ago
  14. geoffb Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    Right, so you were right with 16; it is an extraneous root.

    • one year ago
  15. savvers Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    yeah it looks like that then and thanks man

    • one year ago
  16. geoffb Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    Hey, no problem. :)

    • one year ago
    • Attachments:

See more questions >>>

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.