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C2 geometric series

The second and fourth terms of a geometric series are 7.2 and 5.832 respectively.
The common ratio of the series is positive.
For this series, find

(a) the common ratio

I got 2 euqations up, ar=72, and ar^3 = 5.832

but i try to make like terms in one equation to work out r, it does'nt work :s-smilie:

(b) the first term

I cant re-arrange the eq sufficiently :s-smilie:

please help.

thanks! :smile:
Reply 1
T_Bag
The second and fourth terms of a geometric series are 7.2 and 5.832 respectively.
The common ratio of the series is positive.
For this series, find

(a) the common ratio

I got 2 euqations up, ar=72, and ar^3 = 5.832

but i try to make like terms in one equation to work out r, it does'nt work :s-smilie:

(b) the first term

I cant re-arrange the eq sufficiently :s-smilie:

please help.

thanks! :smile:

if you have ar = 72 and ar3 = 5.832, you should be able to solve them simultaneously. click on "show" if you're still stuck.

Spoiler

Or you could just divide one by the other and get r^2 straight off.