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Math Help - addition of ordinates

  1. #1
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    addition of ordinates

    y=x^3 and Z=loge(x+1). Hence, using addition of ordinates, sketch the grph of w=z-y. use domain of (-1,-2].

    please i need help with this what would be the new set of points. i dont get it
    Last edited by Barney; May 30th 2011 at 12:44 AM. Reason: spelling error
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  2. #2
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    You probably mean the segment (-1,2]. (Why do we have to guess?)

    Draw both graphs. Note approximately their intersection points. The difference will be zero in these points. Determine where the difference w is positive and negative. Calculate the value (approximately) of w for x = 0, 1, 2 and very close to -1.

    In general, if you have two points (x, z) and (x, y), then the difference will obviously be (x, z - y). Determine this difference (at least visually and approximately) for any additional x coordinates that you'd like, and then smoothly connect the obtained points of the graph.
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  3. #3
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    hi thankyou so is this what i do to get the points:
    h(x)=loge(1+1)-1^3 = (1,-1)
    h(x)=loge(2+1)-2^3 = (2,-6.90)
    h(x)=loge(0.1+1)0.1^3 = (0.1,0.094)
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  4. #4
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    You need to define h since this is the first time it appears. Let h(x) = z(x) - y(x).

    h(1) = log(1+1) - 1^3; the left-hand side is h(1), not h(x) for some indeterminate x.

    h(1) is a number, it can't equal (1,-1), which is a pair of numbers.

    log(2) - 1 is not -1.

    Calculate h(0) and h(x) for x close to -1 (approximately).
    Last edited by emakarov; May 30th 2011 at 02:25 AM.
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  5. #5
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    h(x)=loge(1+1)-1^3 = (1,1.69)
    h(x)=loge(2+1)-2^3 = (2,-6.90)
    h(x)=loge(0.1+1)0.1^3 = (0.1,0.094)
    h(0)=0
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  6. #6
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    h(1) is still wrong.

    Quote Originally Posted by emakarov View Post
    the left-hand side is h(1), not h(x) for some indeterminate x.
    Quote Originally Posted by emakarov View Post
    h(1) is a number, it can't equal (1,-1), which is a pair of numbers.
    Quote Originally Posted by emakarov View Post
    Calculate... h(x) for x close to -1 (approximately).
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  7. #7
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    oh is it -0.306
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  8. #8
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    After you've done all of the above (note: I did not quote myself automatically), connect the points. You can calculate h(x) for other x's in the same way.
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  9. #9
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    thanks you gun
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  10. #10
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    Also, the maximum will be approximately at x = 0.48.
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  11. #11
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    thankyou heaps
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