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can someone evaluate this for me?

f(x+h)-f(x)/h when f(x) = 1/x^2 + 2

4 Answers

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  • JSAM
    Lv 5
    1 decade ago
    Favorite Answer

    If you take this limit as h->0, this is a derivative problem. Using the product rule, you know that:

    d[x^-2+2]/dx = -2/x^3. Now check if that's what we get for the limit.

    You are given f(x). To evaluate f(x+h), plug in x+h instead of x. Thus, the abouve expression simplifies to:

    [(1/(x+h)^2 + 2) - (1/x^2 + 2)]/h ----> simplifying, you get:

    [1/(x^2+2xh+h^2) - 1/x^2]/h -----> multiply by the common denominator to simplify:

    {[x^2 - (x^2+2xh+h^2)]/[(x^2)(x^2+2xh+h^2)]}/h ----> simplfy to get:

    (-2x-h)/(x^4+2x^3h+x^2h^2)

    This is your desired answer, but if you are looking for the derivative, evaluate this as h->0. Doing this, you get:

    -2/x^3, which is the derivative from above

    -----------

    Hope this helps

  • 1 decade ago

    I assume you're looking for the derivative of 1/x^2+2, which is just -2/x^3.

  • locuaz
    Lv 7
    1 decade ago

    ok:

    [1/(x+h)^2 +2 - (1/x^2 +2 ) ]/h

    = [1/(x+h)^2 - 1/x^2 ] / h

  • 1 decade ago

    f(x+h)-f(x)/h when f(x) = 1/x^2 + 2

    [1/(x+h)^2 +2 - (1/x^2 +2 ) ]/h

    = [1/(x+h)^2 - 1/x^2 ] / h

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

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

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

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

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

    .

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