Asked by Et khaw
The second term of a GP is 81 and the fourth term is 9. Find,
(i) the common ratio,
(ii) the sum of the first terms,
(iii) the sum to infinity.
(i) the common ratio,
(ii) the sum of the first terms,
(iii) the sum to infinity.
Answers
Answered by
Reiny
2nd term is 81 ---- ar = 81
4th term is 9 ----- ar^3 = 9
divide second equation by the first
r^2 = 9/81 = 1/9
r = ± 1/3
so ar = 81
a(1/3) = 81
a = 243
ii) you have a type, but now that you have a and r, whatever the question should be simple
iii) sum of infinite
=a/(1-r) = 243/(1-1/3)
= 243/(2/3)
= 243(3/2) = 364.5
4th term is 9 ----- ar^3 = 9
divide second equation by the first
r^2 = 9/81 = 1/9
r = ± 1/3
so ar = 81
a(1/3) = 81
a = 243
ii) you have a type, but now that you have a and r, whatever the question should be simple
iii) sum of infinite
=a/(1-r) = 243/(1-1/3)
= 243/(2/3)
= 243(3/2) = 364.5
Answered by
Eni
i want to answer this question
Answered by
ify
good answer
There are no AI answers yet. The ability to request AI answers is coming soon!
Submit Your Answer
We prioritize human answers over AI answers.
If you are human, and you can answer this question, please submit your answer.