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Please correct this excercise

  1. Feb 13, 2007 #1
    they ask me to find the average rate of change from x=1 to x=2 in the equation x-2x^2

    this is what I did

    2-2(1)^2/2-1 = 0/1= 0

    is that right?

  2. jcsd
  3. Feb 13, 2007 #2


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    It is difficult to tell just what you did.

    Average rate of change would be something like:

    [tex] \frac {F(x_1) - F(x_2)} { x_1 -x_2} [/tex]

    Your F(x) :

    [tex] F(x) = x - 2x^2 [/tex]

    Keep in mind, that x is common in that expression, the first x must equal the 2nd x.
  4. Feb 14, 2007 #3


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    What you wrote, even if the calculations are correct, is meaningless.
    First, I suspect you MEAN (2- 2(1)^2)/2- 1, not what you wrote.

    In any case, you need to write "the average rate of change is ... " so someone reading this will know what you are doing.

    What is the value of the function when x= 1?
    What is the value of the function when x= 2?

    What is the change in the value?

    What is the average rate of change?

    It strongly urge you to get into the habit of writing your work one step at a time like that. It will make it clearer to others what you are doing and, hopefully, make more sense to you (and probably give your teacher a heart attack!).
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