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    Hi can someone help me with this question. I don't really get it.

    I've tried finding the ratio and then using that to find a. Then using both values to take away the sum of the terms and sum to infinity. I get no where.

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    (Original post by Federerr)
    Hi can someone help me with this question. I don't really get it.

    I've tried finding the ratio and then using that to find a. Then using both values to take away the sum of the terms and sum to infinity. I get no where.
    Show your working
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    (Original post by RDKGames)
    Show your working
    ar = -48
    ar^4 = 6

    r^-3 = -8
    r = -0.5

    a = -48/-0.5
    a = 96

    Then all I did is put them number in the formula for sum of infinity and series and tried to take them away. Didn't really work it.
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    (Original post by Federerr)
    ar = -48
    ar^4 = 6

    r^-3 = -1/8
    r = -0.5

    a = -48/-0.5
    a = 96

    Then all I did is put them number in the formula for sum of infinity and series and tried to take them away. Didn't really work it.
    Well it should work, it's hard to see where you're going wrong without seeing your working for it.
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    (Original post by RDKGames)
    Well it should work, it's hard to see where you're going wrong without seeing your working for it.
    I don't really know how to find the difference of the 2. Could you please show me.
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    (Original post by Federerr)
    I don't really know how to find the difference of the 2. Could you please show me.
    Take one away from the other.

    \displaystyle \frac{a}{1-r} - \frac{a(1-r^n)}{1-r}=\frac{a}{1-r}(r^n)
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    (Original post by RDKGames)
    Take one away from the other.

    \displaystyle \frac{a}{1-r} - \frac{a(1-r^n)}{1-r}=\frac{a}{1-r}(r^n)
    I still don't get what the questions is asking me too prove. I feel i'm making such a stupid mistake. Hold up let me try take a pic and upload it.
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    (Original post by Federerr)
    I still don't get what the questions is asking me too prove. I feel i'm making such a stupid mistake. Hold up let me try take a pic and upload it.
    C'mon Rog, this is way easier than it is to win 18 slams

    It's just asking you to compute the difference between the first n terms and the sum to infinity (and you know the formula for each of those things). That's all.
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    (Original post by RDKGames)
    Take one away from the other.

    \displaystyle \frac{a}{1-r} - \frac{a(1-r^n)}{1-r}=\frac{a}{1-r}(r^n)
    So how is 64(-0.5^n) the same as 2^6-n
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    (Original post by Indeterminate)
    C'mon Rog, this is way easier than it is to win 18 slams

    It's just asking you to compute the difference between the first n terms and the sum to infinity (and you know the formula for each of those things). That's all.
    Haha, It's a Friday night. I doubt most people do school work at this time haha. I just need to start preparing for mocks

    My mind can't currently completely simple arithmetics
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    (Original post by Federerr)
    So how is 64(-0.5^n) the same as 2^6-n
    64 and 0.5 are both powers of 2.
 
 
 
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