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anonymous

  • one year ago

find the derivative of f(x) = -3/x at x=-4

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  1. anonymous
    • one year ago
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    I got 3/4 but im not sure if that is correct?

  2. dessyj1
    • one year ago
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    did you find the derivative of f(x)

  3. anonymous
    • one year ago
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    How would you do that? Would it be |dw:1434601306329:dw|

  4. dessyj1
    • one year ago
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    no, not quite. You are finding the derivative by using the definition of a derivative. Have you learned the short hand way of finding derivatives by using the the derivative rules?

  5. anonymous
    • one year ago
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    Would you do the power rule?

  6. dessyj1
    • one year ago
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    You would use the quotient rule

  7. anonymous
    • one year ago
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    I dont know what that is

  8. dessyj1
    • one year ago
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    |dw:1434601640378:dw| ring a bell?

  9. dessyj1
    • one year ago
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    if it does not that is fine, we can work with the definition of a derivative.

  10. dessyj1
    • one year ago
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    |dw:1434601759504:dw| is where you would begin.

  11. anonymous
    • one year ago
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    oh i just forgot to put it over h

  12. dessyj1
    • one year ago
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    then get the numerators to a common denominator

  13. anonymous
    • one year ago
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    ok so you get (-3/x^2+xh - 3/x^2+xh) / h

  14. anonymous
    • one year ago
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    which becomes (-6/x^2+xh ) / h ?

  15. dessyj1
    • one year ago
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    you forgot to multiply the top by what the value with which you multiplied the bottom

  16. dessyj1
    • one year ago
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    at the last step, you were supposed to get ((-3x/x^2+xh)-(-3(x+h)/x^2+xh))/h

  17. dessyj1
    • one year ago
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    |dw:1434602235743:dw|

  18. anonymous
    • one year ago
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    Use L'Hopital's Rule to find derivative, then plug in -4. L'Hopital's Rule: (denominator * derivative of top)- (numerator * derivative of bottom)/(denominator^2) Derivative of -3/x= 3/x^2 Plug in (-4) = 3/16

  19. anonymous
    • one year ago
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    |dw:1434602370201:dw| |dw:1434602394506:dw|

  20. dessyj1
    • one year ago
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    |dw:1434602511993:dw| If you simplified everything correctly you should get

  21. anonymous
    • one year ago
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    Thanks!!

  22. dessyj1
    • one year ago
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    we are not done

  23. dessyj1
    • one year ago
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    now you have to cancel out the h and evaluate the limit to find your derivative, or did you use the other guy's method?

  24. dessyj1
    • one year ago
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    elysecollinsm=other guy

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