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anonymous

  • one year ago

Find the sum of the infinite series 4 + 3.2 + 2.56 + 2.048 +...if it exists.

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  1. anonymous
    • one year ago
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    @Loser66 can u help?

  2. anonymous
    • one year ago
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    i cant remeber what the formula for sum is

  3. anonymous
    • one year ago
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    Sn=a1*1-n/1-n i think?

  4. welshfella
    • one year ago
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    this is a geometric series sum to infinity = 1 / (1 - r) where a = frist term and r = common difference

  5. welshfella
    • one year ago
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    sorry that' s a / (1 - r)

  6. welshfella
    • one year ago
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    to find r divide 2nd term by first this should equal 3rd / 2nd

  7. anonymous
    • one year ago
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    4/(r-.8)

  8. anonymous
    • one year ago
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    4/(1-.8)

  9. welshfella
    • one year ago
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    yes

  10. anonymous
    • one year ago
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    i got .05

  11. welshfella
    • one year ago
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    you ve gone wrong somewhere = 4 / (1 - 0.8) = 4 / 0.2

  12. anonymous
    • one year ago
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    20

  13. welshfella
    • one year ago
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    thats it

  14. anonymous
    • one year ago
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    how would i know if it doesnt exists?

  15. welshfella
    • one year ago
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    here each term is decreasing - so the sum converges to a certain value If each term was greater than the last the sum would diverge - a limit would not exist

  16. anonymous
    • one year ago
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    okay. can u help me with a few more please? im still trying to get the hang out this

  17. welshfella
    • one year ago
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    eg 2 + 4 + 6 diverges

  18. welshfella
    • one year ago
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    ok

  19. anonymous
    • one year ago
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    should i ask here or open a new post

  20. welshfella
    • one year ago
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    best to open a new post

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spraguer (Moderator)
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