Question

Geometric sequence: an=3(1/2)^(n-1)
First term is 3 and common ratio is 1/2.
Find sum of the first 3 terms, or S3. Either add the first 3 terms or use the formula:
Sn=a1-a1^r^n/1-r. Help on how to do this?! Please!

Answer 1

Use this formula:
Sn=a1-a1^r^n/1-r, but just rewrite it what is that?
Sn = (a1-a1^r)^n/(1-r) ?

Answer 2

Yes, the one you typed is correct.

Answer 3

a1 = 3
r = 1/2
n=3
S3 = ?

Answer 4

Substitue all the values u have for Sn formula, wehre
a1=3
r=1/2
n=3

Answer 5

O.k, thank you so much :)