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Homework Help: Math Help

  1. Jan 21, 2005 #1
    Estimate the area under the graph of f(x) =x^2 + 4x from x=1 to x=9 using 4 approximating rectangles and left endpoints.

    first i had to find delta x, so i did 9-1/4 = 2
    which means x0 = 0, x1 = 2, x2= 4, x3=6 (since i'm using left endpoints, i include x0)

    after that, i just plug it in the left end point formula:
    L4 = 2*0 + 2*12 + 2*32 + 2*60 = 208

    i done the calculations many time and get the same answer, am i missing something?
  2. jcsd
  3. Jan 21, 2005 #2
    the x's should be 1,3,5,7... you started at 1
  4. Jan 21, 2005 #3
    ah, i see. thanks for the help.
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