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Math Help - differentation

  1. #1
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    differentation

    hi,

    i nned to know how to differentiate this;

    y=3x^2-4x+1

    i have dy/dx= -9x^-4+8x+1

    would this be correct or would i not keep the +1 on the end?

    thanks!
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  2. #2
    MHF Contributor Siron's Avatar
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    Re: differentation

    Is this the function you have to differentiate:
    y=3x^2-4x+1
    ?

    Maybe you should split up in terms and calculate the derivative of each term.
    Do you know the derivative of a constant number? ...
    Do you know this rule:
    D(x^n)=n\cdot x^{n-1}? ...
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  3. #3
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    Re: differentation

    basically what i did was:
    3x^-3=-9x^-4, times the 3 and -3 together and take away one power
    same with 4 and 2, times them to get 8 and take away one power to get 8x.

    so now i have dy/dx= -9x^-4+8x but i don't know if i keep the +1 or not?
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  4. #4
    MHF Contributor Siron's Avatar
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    Re: differentation

    I can't follow why you're calculating derivatives like that.
    Do you understand that:
    \frac{d(3x^2)}{dx}=6x
    ?
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  5. #5
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    Re: differentation

    no i don't understand, im just going by what my teacher has told us and how i have done them before.
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  6. #6
    MHF Contributor Siron's Avatar
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    Re: differentation

    Ok, no problem we will figure it out.
    How would you calculate:
    \frac{d(3x^2)}{dx}= ...
    ?
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  7. #7
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    Re: differentation

    i don't know.
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  8. #8
    MHF Contributor Siron's Avatar
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    Re: differentation

    Maybe you should talk with your teacher about this and take soms lessons, because I think it's really difficult to explain everything about calculating derivatives via the pc.
    What have you learned yet at school about derivatives? ...
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  9. #9
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    Re: differentation

    we have basically learn what i have done to sole the question, but i was unsure if it was correct. i will try and see her soon to discuss it! thanks for the help anyway though!
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  10. #10
    MHF Contributor Siron's Avatar
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    Re: differentation

    You're welcome and it's looks indeed a good idea to go to your teacher .
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  11. #11
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    Re: differentation

    Quote Originally Posted by andyboy179 View Post
    i don't know.
    The formula given at the end of post #2 (and which will undoubtedly be in your class notes and textbook) tells you exactly how to do it.
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