Quantcast

A community for students.

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

Christos

  • 2 years ago

Limits, Can you help me find out this specific thing I dont know how to find out http://screencast.com/t/PUvesX4N

  • This Question is Closed
  1. agent0smith
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 2

    Once you find f'(x), plug in a to get the slope of the line, m. Then you want to get it in the form y=mx+b, by using the fact it passes through the point (a, f(a))

  2. BTaylor
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Do you know how to take the derivative? If so, then first take the derivative of the function, then evaluate it at the given a -- this is "m", the slope of the tangent line. Now, evaluate the function at the given a. This we'll call "y1" The tangent line is: y-y1 = m (x-a)

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

    Can please someone tell me what is a slope just so I get the bigger picture of whats going on?

  4. agent0smith
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 2

    Slope is the steepness of the line, or rate of change. Remember back in algebra, equations y=mx+b have a slope of m.

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

    @BTaylor what do you mean by "Now, evaluate the function at the given a. " ?

  6. BTaylor
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    so, for number 9, f(x) = 2x^2. The given "a" is 1. So evaluating the function at a means you plug in a for x, and get 2(1)^2, which is 2.

  7. agent0smith
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 2

    That means plug in x=1 (since a=1) into f = 2x^2

  8. BTaylor
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    @agent0smith is right. To visualize this tangent line, click this link: http://www.wolframalpha.com/input/?t=crmtb01&f=ob&i=tangent%20line%20to%202x%5E2%20at%20x%3D1

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

    I got y1 = 0

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

    y1 = -2

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

    y1 = 2 :D **

  12. BTaylor
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    the last one is right. y1 = 2.

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

    so that's the answer?? y1 = 2 and I am done? Nothing else needed?

  14. agent0smith
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 2

    No... did you find the slope?

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

    its 4

  16. BTaylor
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    yes. because the derivative is 4x, evaluated at x=1 gives you 4(1) =4

  17. agent0smith
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 2

    So then put it in point-slope form: y-y1 = m (x-x1) where x1 = 1, y1= 2

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

    yea

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

    I did all that and I got y1 = 2 in the end, I am done ?

  20. agent0smith
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 2

    Wait, no, where is your x going? y-y1 = m (x-a) y - 2 = 4(x-1)

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

    x-1 = 0

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

    x = 1

  23. agent0smith
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 2

    x is x.

  24. agent0smith
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 2

    a is 1.

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

    then why y is not y too and had to be replaced

  26. agent0smith
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 2

    y is y. y-2 = 4 (x-1)

  27. agent0smith
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 2

    You're using point slope form to write the equation of a line: http://www.purplemath.com/modules/strtlneq2.htm

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

    Nice! I see now! Thank you both! I wish I could give more medals!

  29. agent0smith
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 2

    Your line has a slope of m=4, and passes through the point (1, 2) then you just plug it into the point slope formula.

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

    oh i see

  31. agent0smith
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 2

    And again, this is what you have found: http://www.wolframalpha.com/input/?t=crmtb01&f=ob&i=tangent%20line%20to%202x%5E2%20at%20x%3D1

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

    yes

  33. 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.