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anonymous

  • one year ago

CALCULUS: STATIONARY POINT \[f(x)=x^3+Ax+B\] has a stationary point at (-2, 3). Find the values of A & B. --- I've already found A=-12. I just don't know how to find B.

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  1. Zale101
    • one year ago
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    what does it mean if the function has a stationary point?

  2. Zale101
    • one year ago
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    Stationary point means the derivative of that function is zero.

  3. anonymous
    • one year ago
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    Well, I just know that if a function has a stationary point then the derivative of that function is equal to 0.

  4. anonymous
    • one year ago
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    oh... you already said that lol

  5. Zale101
    • one year ago
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    Did you find b already or not?

  6. anonymous
    • one year ago
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    Nope, not yet.

  7. anonymous
    • one year ago
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    I don't know what to do.

  8. anonymous
    • one year ago
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    Should I just plug in (2,3) to the function to solve for B?

  9. anonymous
    • one year ago
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    If so, then I'll get B=-13. But I'm not sure.

  10. anonymous
    • one year ago
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    this is not just about plugging in values you need to know what you're doing and why you're doing it

  11. anonymous
    • one year ago
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    Yeah, that's why I am asking how to do it. :)

  12. Zale101
    • one year ago
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    You should start with taking the derivative, set it equal to zero

  13. anonymous
    • one year ago
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    how should not be the point of interest

  14. anonymous
    • one year ago
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    Okay, I'll show my work.

  15. Zale101
    • one year ago
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    set x=-2 and f(x) =3

  16. anonymous
    • one year ago
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    ^ that's what I did to find B.

  17. anonymous
    • one year ago
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    |dw:1442978733930:dw|

  18. Jhannybean
    • one year ago
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    Hmm..I don't think you can just leave out B

  19. anonymous
    • one year ago
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    we know that in a graph |dw:1442978750479:dw|

  20. Zale101
    • one year ago
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    a and b are constants...

  21. anonymous
    • one year ago
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    @Jhannybean Well, B is a constant. SO the derivative is 0.

  22. Jhannybean
    • one year ago
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    Oh, didn't see the derivative sign in your function, m'bad.

  23. anonymous
    • one year ago
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    You didn't? That's fine. :D

  24. Zale101
    • one year ago
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    After you solve for a and got -12 plug that to the original equation and dont forget to plug (-2,3) for x and f(x). From there, you can solve for b.

  25. anonymous
    • one year ago
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    ^ I did that and I got -13.

  26. anonymous
    • one year ago
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    just like what I said a while ago :D

  27. Zale101
    • one year ago
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    Okay, then you are good to go :)

  28. anonymous
    • one year ago
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    Awesome! Thanks for the help though! :)

  29. Zale101
    • one year ago
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    Anytime!

  30. anonymous
    • one year ago
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    I actually just found out that stationary points are critical points based on this problem. I heart openstudy

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