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math- Algebra 2

posted by on .

I have absolutely no idea how to do this please help!
Find the sum:
it has the sigma sign with 12 at the top, (10k-8)(6k+7) in the middle and k=1 at the bottom

  • math- Algebra 2 - ,

    It just means, add:

    the value of (10k-8)(6k+7) when k=1
    plus
    the value of (10k-8)(6k+7) when k=2
    plus
    the value of (10k-8)(6k+7) when k=3
    plus
    ... (and so on, 4, 5, to 9, 10)...
    the value of (10k-8)(6k+7) when k=11
    plus
    the value of (10k-8)(6k+7) when k=12

    So you could just do it by calcuating out:

    the value of (10k-8)(6k+7) when k=1 is 26
    plus
    the value of (10k-8)(6k+7) when k=2 is 228

    and so on.

    It mightn't be a bad idea to do that anyway, since you will understand it thoroughly and be sure of your answer.

    However, there are short-cuts.

    It may be that you've already covered these in your class, or it may be that you were given this exercise so that you'll appreciate them when you do cover them! :-)

    There is a formula for the sum of x from 0 to n and a formula for the sum of x^2 from 0 to n. You can probably find them in your text.

    By multiplying out the expression, we can then use those formulas.

  • math- Algebra 2 - ,

    all right great thank you so much!

  • math- Algebra 2 - ,

    You're welcome!

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