00:01
So in our geometric sequence, we want the first term to be two, and we want the common ratio to be three.
00:08
And we want to find a sub five and a sub n.
00:12
We could find a sub n to begin with, but let's just write down some terms.
00:16
So we know a1 is equal to two.
00:18
We know a sub two is equal to two times three, which will be six.
00:26
And then if we find a sub three, all we have to do is multiply by six again.
00:30
Excuse me, multiply by three again, which is going to be the previous term times 18.
00:37
Not times 3 is 18.
00:39
A sum 4 is going to end up being two times the third term times one more three, which is going to be 54.
00:50
And then the fifth term is going to be two times, this previous term, two times three times three...