# Math Help - geometric sequence help

1. ## geometric sequence help

List the first four terms of a geometric sequence with t1 = 4 and tn = -3tn-1.
How do I find r???

2. ## Re: geometric sequence help

Originally Posted by dzomberg
List the first four terms of a geometric sequence with $t_1 = 4$ and $t_n = -3t_{n-1}$.
How do I find r???
Well $t_2=-3(t_1)$. Now you post what you get!

3. ## Re: geometric sequence help

Hello, dzomberg!

List the first four terms of a geometric sequence with:- $t_1 = 4\,\text{ and }t_n = \text{-}3\!\cdot\!t_{n-1}$

How do I find $r$?

Just read what you are given . . . and crank out the list.

$t_1 = 4$ . . . The first term is 4.

$t_n = \text{-}3\!\cdot\!t_{n-1}$ . . . Each term is -3 times the preceding term.

Therefore:

. . $\begin{array}{cccccc}t_1 &=& 4 &=& \;4\\ t_2 &=& \text{-}3(4) &=& \text{-}12 \\ t_3 &=& \text{-}3(\text{-}12) &=& \;36 \\ t_4 &=& \text{-}3(36) &=& \text{-}108 \end{array}$

4. ## Re: geometric sequence help

Originally Posted by dzomberg
List the first four terms of a geometric sequence with t1 = 4 and tn = -3tn-1.
How do I find r???
....And please learn to use LaTeX (as in our LaTeX help forum) or learn how to use parenthesis. tn = -3t(n-1) is a bit better anyway. t_n = -3t_(n - 1) would be best.

-Dan