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

mathcalculus Group Title

hello guys, can someone help me with related rates? (attached)

  • one year ago
  • one year ago

  • This Question is Closed
  1. Psymon Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    Eww, word problems *waits for the problem and prepares sword*

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

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

    Oh, not a word problem :D okay, np with this one

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

    So whenever you take the derivative of y, you can mark it with (dy/dx). Whenever you take the derivative of an x, you can mark it with (d/dx). So take the derivative of both sides, put dy/dx and d/dx where necessary, and plug in the given values.

    • one year ago
  5. zzr0ck3r Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    the derivative of 7x^3 - 10x with respect to t Is 0

    • one year ago
  6. pgpilot326 Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    dx/dt = 0 so will dy/dt

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

    alright let me try this step by step.

    • one year ago
  8. zzr0ck3r Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    y is in terms of x, there are no t's so treat x's like a constant derivative of a constant is 0

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

    Pretty much. They made it a little easy on ya with there being a dx/dt, haha. But itd be nice practice if we said it was d/dx and made d/dx equal to 1.

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

    okay so the derivative to this would be: 21x^2-10

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

    Correct.

    • one year ago
  12. zzr0ck3r Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    with respect to x, yes but they ask for it with respect to t (not x)

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

    okay. so do i multiply each by dx/dt?

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

    Its like theyre saying, there is no t for there to be a derivative in respect to, so everything is 0. Thats why I said we should change the conditions of the problem for practice.

    • one year ago
  15. zzr0ck3r Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    \[\frac{d(f(x))}{dt}=0\]

    • one year ago
  16. pgpilot326 Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    x is some function of t, thus when we take the derivative of y with respect to t, we get \[\frac{ dy }{ dt }=\frac{ d }{ dt }\left( 7x ^{3}-10x \right)=\frac{ d }{ dt }\left( 7x ^{3} \right)-\frac{ d }{ dt }\left( 10x \right)=21x ^{2}\frac{ dx }{ dt }-10\frac{ dx }{ dt }\]form there it's plug in what you know and compute

    • one year ago
  17. pgpilot326 Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    since dx/dt is 0, dy/dt is 0. y only depends on x. look at te function. if x doesn't change, neither will y. the math proves it.

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

    question: why would it be zero?

    • one year ago
  19. pgpilot326 Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    the problem states that dx/dt = 0

    • one year ago
  20. pgpilot326 Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    each term in dy/dt is multiplied by dx/dt

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

    and dy/dt= d/dt?

    • one year ago
  22. pgpilot326 Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    no, d/dt is an operator. it says take the derivative of wht follows with respect to t.

    • one year ago
  23. pgpilot326 Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    dy/dt is the derivative of y with respect to t.

    • one year ago
  24. pgpilot326 Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    do you know the chain rule for derivatives?

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

    sort of, I need to refresh my memory with the chain rule.

    • 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.