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Math Help - Algebra problem...

  1. #1
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    Algebra problem...

    For h ≠ 0, which of the following is equivalent to

    <br />
(A(x+h)^2-Ax^2)/h<br />
?

    i have 5 answers...
    a) 2Ax + Ah
    b) Ax + Ah
    c) 2Ax + Ah^2
    d) Ah
    e) 2Ax

    How would I go about solving this problem?
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  2. #2
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    May 2009
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    expand the numerator

    (x+h)^2=x^2+2h+h^2 now multiply that by A, combine like terms, factor to cancel an h, and you'll have your answer
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  3. #3
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    Jun 2009
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    Quote Originally Posted by JAMESveeder View Post
    For h ≠ 0, which of the following is equivalent to

    <br />
(A(x+h)^2-Ax^2)/h<br />
?

    i have 5 answers...
    a) 2Ax + Ah
    b) Ax + Ah
    c) 2Ax + Ah^2
    d) Ah
    e) 2Ax

    How would I go about solving this problem?
    \frac{(A(x+h)^2 - Ax^2)}{h} = \frac{A(x^2 + 2xh + h^2) - Ax^2}{h}

    = \frac{A(x^2 + 2xh + h^2 - x^2)}{h}

    You should be able to take it from here.

    If you didn't already know, it seems this question was asked with the aim of introducing you to calculating derivatives from first principles, in this case the derivative of Ax^2. To find the derivative of the function you take the limit as h tends to zero:

    \frac{d}{dx} Ax^2 = \lim_{h \to 0} \frac{(A(x+h)^2 - Ax^2)}{h} = \lim_{h \to 0} (2Ax + Ah) = 2Ax

    as you would expect.

    Hope this helped,
    pomp.
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