The sum of the first 3 terms of a geometric series is 171 and the common ratio is 2/3.

What is the first term of the series?

I Don't know what to do- it says I have to use formula?

tommarvoloriddle Aug 6, 2019

#1

#3**+2 **

\(\text{well then you should know that the sum of the first three terms are}\\ a + \dfrac 2 3 a + \dfrac 4 9 a = \dfrac{19}{9}a = 171\\ a=81\)

Rom
Aug 6, 2019

#4**+2 **

ok, thank you, Rom!

I got that answer too, I just forgot to post it...

tommarvoloriddle
Aug 6, 2019