Quantcast

A community for students.

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

Val97

  • 2 years ago

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

  • This Question is Closed
  1. amistre64
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    sooo, you need help adding? or is it that you really need help in determining all the 8 terms?

  2. amistre64
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    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.

  3. Notamathgenius
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Fine out what the term is going up by. I see -4

  4. Val97
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    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?

  5. amistre64
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    formulas are only half the battle. seeing a pattern is the key once you see that pattern, the formula is known by default

  6. Val97
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    So that is it? Its isn't any of the formulas they gave me?

  7. amistre64
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    if you subtract 4 from the last term given, what do you get?

  8. Val97
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    -15, -19, -23

  9. amistre64
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    .... 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

  10. amistre64
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    but yes ..., -15, -19, -23, -27 fill in all 8 terms

  11. amistre64
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    \[\frac{n}{2}(a_1+a_8)=sum\]

  12. Val97
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    ok got it! thanks!

  13. amistre64
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    youre welcome, good luck :)

  14. Not the answer you are looking for?
    Search for more explanations.

    • Attachments:

Ask your own question

Sign Up
Find more explanations on OpenStudy
Privacy Policy

Your question is ready. Sign up for free to start getting answers.

spraguer (Moderator)
5 → View Detailed Profile

is replying to Can someone tell me what button the professor is hitting...

23

  • Teamwork 19 Teammate
  • Problem Solving 19 Hero
  • You have blocked this person.
  • ✔ You're a fan Checking fan status...

Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.

This is the testimonial you wrote.
You haven't written a testimonial for Owlfred.