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anonymous

  • one year ago

What are the explicit equation and domain for a geometric sequence with the first term of 5 and a second term of -10?

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  1. anonymous
    • one year ago
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    an=5(-2)^(n-1); all integers when n≥1 an=5(-2)^(n-1); all integers where n≥0 an=5(-15)^(n-1); all integers where n≥1 an=5(-15)^(n-1); all integers where n≥0

  2. anonymous
    • one year ago
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    @ganeshie8

  3. anonymous
    • one year ago
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    @phi

  4. anonymous
    • one year ago
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    @dan815

  5. anonymous
    • one year ago
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    yay @phi is here

  6. anonymous
    • one year ago
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    I'm pretty sure the second half is n≥1

  7. anonymous
    • one year ago
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    right?

  8. phi
    • one year ago
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    You could test each choice. You should get 5, -10 as the first two numbers.

  9. anonymous
    • one year ago
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    a

  10. anonymous
    • one year ago
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    wait

  11. anonymous
    • one year ago
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    b

  12. anonymous
    • one year ago
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    no a

  13. anonymous
    • one year ago
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    omg im so confused

  14. phi
    • one year ago
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    ***an=5(-2)^(n-1); all integers when n≥1*** for n=1 you get \[ a_1 = 5(-2)^{1-1} \\ a_1 = 5\cdot (-2)^0 \] anything to the zero power is 1 , so that simplifies to \[ a_1= 5 \cdot 1 \\a_1=5\] that looks good so far

  15. phi
    • one year ago
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    now find a2 for choice A, using n=2

  16. anonymous
    • one year ago
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    a2=5(-2)^(2-1) =5(-2)^1 =-10

  17. phi
    • one year ago
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    yes. so choice A looks like the answer. You could double check the other three, but they won't work (give 5, -10)

  18. anonymous
    • one year ago
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    ok thank you i have another but i don't know how to post the graphs so oh well

  19. phi
    • one year ago
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    do you know how to take a screen shot?

  20. anonymous
    • one year ago
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    the wording is horrible

  21. anonymous
    • one year ago
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    yeah put its on my other computer hang on

  22. anonymous
    • one year ago
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    It says which logarithmic graph can be used to approximate the value of y in the equation 2^y=3

  23. anonymous
    • one year ago
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    i don't know how to log that?

  24. phi
    • one year ago
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    take the log of both sides. Log base 2 is the most convenient, but log base 10 or log base 3 (natural log) all can be used. use the "rule" \[ \log(a^b) = b \log(a) \]

  25. anonymous
    • one year ago
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    so… log10 2^y= log10 3

  26. phi
    • one year ago
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    and then use the rule to write \[ y \log 2 = \log 3 \\ y = \frac{\log 3}{\log 2} \]

  27. phi
    • one year ago
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    to get the answer from a graph, we need to figure out what log base they used. for example, what is the x value that corresponds to y=1 (that should give us the base)

  28. phi
    • one year ago
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    Here are 3 possible logs if they gave you log base 2, read off the y value at x=3

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  29. anonymous
    • one year ago
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    thank you i got it

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