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Math Help - sequence?

  1. #1
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    sequence?

    I need some help with sequence and figuring out an equation for given sequence.

    For example,

    what is a equation for a sequence 10,6,10,6,...

    another one is -1/4,-2/9,-3/16/-4/25
    for this one I thought it would be -(n+1)/(n+2)^2 But i got it wrong.

    third one is a1 = 10, a(n+1) = an/(an+1). how would u find a2, a3, a4, a5 from the give information?

    Thanks.
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  2. #2
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    Quote Originally Posted by shah4u19 View Post

    third one is a1 = 10, a(n+1) = an/(an+1). how would u find a2, a3, a4, a5 from the give information?

    Thanks.
    a_1=10

    a_2=a_{1+1}=\frac{a_1}{a_1+1}=\frac{10}{11}

    a_3=a_{2+1}=\frac{a_2}{a_2+1}= ..

    etc.

    CB
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  3. #3
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    Quote Originally Posted by shah4u19 View Post

    another one is -1/4,-2/9,-3/16/-4/25
    for this one I thought it would be -(n+1)/(n+2)^2 But i got it wrong.
    HI

    -\frac{1}{4} , -\frac{2}{9} , -\frac{3}{16} , -\frac{4}{25}

    The nth term of this sequence is -\frac{r}{(r+1)^2} , where r=1,2,3 ...
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  4. #4
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    thanks for your reply. does anyone know 1st one about 10,6,10,6,...?
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  5. #5
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    Quote Originally Posted by shah4u19 View Post
    thanks for your reply. does anyone know 1st one about 10,6,10,6,...?
    a_n=\begin{cases}<br />
10 & n \text{ even }\\<br />
6 & n \text{ odd }<br />
\end{cases}

    CB
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  6. #6
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    no there is only 1 equation for the sequence....thanks anyways...
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  7. #7
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    Quote Originally Posted by shah4u19 View Post
    no there is only 1 equation for the sequence....thanks anyways...
    a_n = 8 + 2 \cdot (-1)^{n+1}
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