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bmelyk

  • 2 years ago

Find the derivative of f(x) =2x^2-1/x^2 in three ways : (a) using the quotient rule (b) using the product rule (c) using neither the product rule nor the quotient rule I have already done all of these out. my answers: a) 2/x^3 b)-4x^3+x+8/2 c)2 for each one I've gotten a different answer, just wondering why. I think I'm supposed to get the same answer each time.

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  1. Mimi_x3
    • 2 years ago
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    is it:\[\frac{2x^2-1}{x^2}\]?

  2. bmelyk
    • 2 years ago
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    yes it is.

  3. CliffSedge
    • 2 years ago
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    Messed up in product rule somewhere.

  4. CliffSedge
    • 2 years ago
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    Maybe double-check your exponents.

  5. Algebraic!
    • 2 years ago
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    uhm.

  6. Algebraic!
    • 2 years ago
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    :)

  7. CliffSedge
    • 2 years ago
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    For product rule start with f(x) = (2x^2-1)(x^-2) Then it's 'first times the derivative of the second, plus the second times the derivative of the first.'

  8. bmelyk
    • 2 years ago
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    i know the formula.

  9. Algebraic!
    • 2 years ago
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    non-quotient-or-product-rule way would be: 2x^2/x^2 - 1/x^2 =2 -1/x^2 (2 -1/x^2)' = - (-2*x^-3)

  10. bmelyk
    • 2 years ago
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    now i re-did it and got 2/x

  11. bmelyk
    • 2 years ago
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    for the third way i did the definition of the derivative and i only got a 2

  12. CliffSedge
    • 2 years ago
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    You're losing track of an exponent somewhere. What are you getting for the derivative of x^-2 ?

  13. bmelyk
    • 2 years ago
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    i re-did the product rule and got 2/x

  14. Algebraic!
    • 2 years ago
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    ur doing it wrong.

  15. bmelyk
    • 2 years ago
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    okay i got a and b right now, just wondering why my definition of the derivative one is wrong.

  16. bmelyk
    • 2 years ago
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    i got 2/x^3 for a and b but only 2 for the definition of the derivative.

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