The Student Room Group
Uni students - Complete our survey >>
Uni students - Complete our survey >>
Uni students - Complete our survey >>

Geometric Sequence help!

Does anyone know how to do this question? Any help will be greatly appreciated:smile:

The sum of the first two terms of a geometric series is 1 and the sum its first four terms is 5. If all of its terms are positive, find the first term and the common ratio.
Original post by Celina Davis
Does anyone know how to do this question? Any help will be greatly appreciated:smile:

The sum of the first two terms of a geometric series is 1 and the sum its first four terms is 5. If all of its terms are positive, find the first term and the common ratio.


Let aa be the first term, and rr be the common ratio.

Then a+ar=1a + ar = 1 and a+ar+ar2+ar3=5a+ar+ar^2+ar^3 = 5.

Note that the second one can be rewritten as (a+ar)+r2(a+ar)=5(a+ar) + r^2(a+ar) = 5

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you