List the first four terms of a geometric sequence with t1 = 4 and tn = -3tn-1.
How do I find r???
Hello, dzomberg!
List the first four terms of a geometric sequence with:- $\displaystyle t_1 = 4\,\text{ and }t_n = \text{-}3\!\cdot\!t_{n-1}$
How do I find $\displaystyle r$?
Just read what you are given . . . and crank out the list.
$\displaystyle t_1 = 4$ . . . The first term is 4.
$\displaystyle t_n = \text{-}3\!\cdot\!t_{n-1}$ . . . Each term is -3 times the preceding term.
Therefore:
. . $\displaystyle \begin{array}{cccccc}t_1 &=& 4 &=& \;4\\ t_2 &=& \text{-}3(4) &=& \text{-}12 \\ t_3 &=& \text{-}3(\text{-}12) &=& \;36 \\ t_4 &=& \text{-}3(36) &=& \text{-}108 \end{array}$
....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