# Math Help - sequence?

1. ## 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.

2. Originally Posted by shah4u19

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

3. Originally Posted by shah4u19

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 ...

5. Originally Posted by shah4u19
$a_n=\begin{cases}
10 & n \text{ even }\\
6 & n \text{ odd }
\end{cases}$

CB

6. no there is only 1 equation for the sequence....thanks anyways...

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