SOLUTION: please help to solve the following the sum of the first and the third terms of a geometric progression is 40. the sum of the second and the fourth terms is 120. Determine the f

Question 859437: please help to solve the following
the sum of the first and the third terms of a geometric progression is 40. the sum of the second and the fourth terms is 120. Determine the first term and the common ratio of the progression.
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
the terms will be
a,ar,ar^2,ar^3
Condition I
a+ar^2=40
a*(1+r^2)=40
(1+r^2) =40/a
condition II
ar+ar^3=120
ar(1+r^2)=120
ar(40/a) =120
40r =120
r=3
plug r to get a
RELATED QUESTIONS
the sum of the first and the third terms of a geometric progression is 40. the sum of the (answered by mananth)

The sum of the second and the third terms of a geometric progression is 6,the sum of the... (answered by Fombitz,Edwin McCravy)

A geometric progression has 6 terms. The first term is 192 and the common ratio is 1.5.... (answered by greenestamps)

A geometric progression has six terms. The first term is 486 and the common ratio is ;.... (answered by greenestamps)

The first term of an arithmetic progression is 12 and the sum of the first 16 terms is... (answered by greenestamps)

find a geometric progression of four terms in which the sum of the first and last terms... (answered by josgarithmetic)

A geometric progression and an arithmetic progression have the same first term. The... (answered by htmentor)

In a geometric progression,the 6th term is 96 and the common ratio is -2. Find the sum of (answered by ikleyn)

find the first 3 terms of a geometric progression whose sum is 42 and whose product is... (answered by htmentor)