SOLUTION: the 3rd term of a Gp is 10 and the 6th term is 80.
find
1. the Gp
2. the nth term of the Gp hence
3. the 9th term
Algebra ->
Sequences-and-series
-> SOLUTION: the 3rd term of a Gp is 10 and the 6th term is 80.
find
1. the Gp
2. the nth term of the Gp hence
3. the 9th term
Log On
You can put this solution on YOUR website! the 3rd term of a Gp is 10 and the 6th term is 80.
find
1. the Gp
------
ar^2 = 10
ar^5 = 80
---------------
Divide bottom equation by top to get:
r^3 = 8
r = 2
-----
Then solve for "a"::
a*2^2 = 10
a = 10/4 = 5/2
-----------------
Gp:: (5/2)*2^(n-1) for n = 1,2,3...
------------------
2. the nth term of the Gp hence::a(n) = (5/2)*2^(n-1)
-------------------
3. the 9th term :: (5/2)2^8 = 640
=============
Cheers,
Stan H.
------------
(