Question

Find the first 5 terms of the sequence: a1 = 2, an = -3an-1

-2, -6, -18, -54, -162
-2, 6, -18, 54, -162
2, 6, 18, 54, 162
2, -6, 18, -54, 162

Answer 1

I am quite confused on the n-1

Answer 2

if I have n =5, then my item is \(a_5\)
so that n-1 =?

Answer 3

4?

Answer 4

ye, , then my item is?

Answer 5

what's wrong?
n=5 ----> I have \(\Large a_5\)
n-1 =4--> I have \(\Large a_?\)

Answer 6

oh... *facepalm* a4

Answer 7

?

Answer 8

hahahaha... YES

Answer 9

now, you have a1 =2 , we can get rid of the first 2 options, right?

Answer 10

yes because they are -2

Answer 11

Next check \(\Large a_{last} \) which is \(\Large a_5\), and consider its previous item,
I pick the third option to check
\(\Large a_5 = 162\) Does it equal to its previous item *-3 ?
I mean -3*54 = 162?

Answer 12

wait im just wondering... just so i know 5-1=4 so you would multiply 4 by 3 and get 12? is that what the whole n-1 is?

Answer 13

nope!!
n, n-1, n-2 which stick with a (a1, a2.....an) to show the order of the item, not the value of the item
for example, the first item \(a_1\) is the guy stands in the front of the series, period.
the value of that guy is -2 (for the first option)
and the first guy of the third option has the name \(a_1\) too, but it value is 2
Different things

Answer 14

got me?