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anonymous

  • one year ago

Which of the following is the formula for the geometric sequence? 320, 80, 20, 5,... an = 320(1/4)n-1 an = 320(4)n-1--- an = 4(320)n-1 I think its the second one?

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  1. butterflydreamer
    • one year ago
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    geometric series: |dw:1434671631437:dw|

  2. butterflydreamer
    • one year ago
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    so firstly, can you tell me what a1 (the first term) is?

  3. anonymous
    • one year ago
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    no

  4. butterflydreamer
    • one year ago
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    "first" term in your sequence: 320, 80, 20, 5,... what's the first number? That's your first term ...

  5. anonymous
    • one year ago
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    320

  6. butterflydreamer
    • one year ago
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    yes that's correct. Now find r (common ratio) by dividing the second term (80) by the first term (320) ... SO r = 80/ 320 = 1/4 Now we know a1 = 320, r = 1/4 So plug it into the formula and we get: \[a_n= a_1r^{n-1}\rightarrow a_n =320(1/4)^{n-1}\]

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