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Val97 Group Title

Please Help! Show me how its done please! Find the sum of the first 8 terms of the sequence. 1, -3, -7, -11, ...

  • one year ago
  • one year ago

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  1. amistre64 Group Title
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    sooo, you need help adding? or is it that you really need help in determining all the 8 terms?

    • one year ago
  2. amistre64 Group Title
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    since the numbers are getting smaller, or going negative, ... and they seem fairly close together. We can try to see if they are subtracting a like amount each time.

    • one year ago
  3. Notamathgenius Group Title
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    Fine out what the term is going up by. I see -4

    • one year ago
  4. Val97 Group Title
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    I need help determining all the 8 terms, this is pre cal and it really confuses me. I'm not sure what formula to use. The Arithmetic Sequence formula?

    • one year ago
  5. amistre64 Group Title
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    formulas are only half the battle. seeing a pattern is the key once you see that pattern, the formula is known by default

    • one year ago
  6. Val97 Group Title
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    So that is it? Its isn't any of the formulas they gave me?

    • one year ago
  7. amistre64 Group Title
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    if you subtract 4 from the last term given, what do you get?

    • one year ago
  8. Val97 Group Title
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    -15, -19, -23

    • one year ago
  9. amistre64 Group Title
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    .... or if you want to create an expression to use in summation thats fine too \[\sum_{n=a}^b~a_1+d(n-1)\] \[\sum_{n=a}^b~a_1+\sum_{n=a}^bd(n-1)\] \[a_1(b-a)+d\sum_{n=a}^bn-1\] \[a_1(b-a)+d\sum_{n=a}^bn-d\sum_{n=a}^b1\] \[a_1(b-a)+d\sum_{n=a}^bn-d(b-a)\] stuff like that

    • one year ago
  10. amistre64 Group Title
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    but yes ..., -15, -19, -23, -27 fill in all 8 terms

    • one year ago
  11. amistre64 Group Title
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    \[\frac{n}{2}(a_1+a_8)=sum\]

    • one year ago
  12. Val97 Group Title
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    ok got it! thanks!

    • one year ago
  13. amistre64 Group Title
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    youre welcome, good luck :)

    • one year ago
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