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Math Help - please help....

  1. #1
    Newbie
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    Oct 2009
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    please help....

    hey we just started doing Derivatives in Math and im a tad bit lost..... i tried reading your calculus introduction section but im having trouble following it .....

    so i have to do this questiong

    F(x) = x^3 + 2x^2 + 4x + 3

    i have to find the derivatives using the first principal and limits

    this formula  f'(x) = (f(x+h) - f(x))/h Where h is approaching 0...i know this is practically asking you the answer but...i dont know how to go about this
    could anyone pleas explain what i need to do.....
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  2. #2
    MHF Contributor Calculus26's Avatar
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    Consider the terms separately

    Hints for f(x) = 2 x^2

    f(x+h) = 2(x+h)^2

    [f(x+h) - f(x)]/h = 2[ (x+h)^2 -x^2]/h = 2[(x+h-x)(x+h+x)]/h
    = 2h(2x+h)/h = 2(2x+h)

    What happens as h ->0 ?


    f(x) = x^3 f(x+h) = (x+h)^3

    [f(x+h)- f(x)]/h = (x+h-x)[(x+h)^2 +(x+h)x + x^2]/h

    = (x+h)^2 +(x+h)x + x^2]

    What happens as h -> 0
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