Asked by asd
The sum of all five terms of an arithmetic sequence is
55. Find the sum of the first three terms of the sequence if the sum of the last three is 48.
55. Find the sum of the first three terms of the sequence if the sum of the last three is 48.
Answers
Answered by
Steve
S5 = 5/2 (2a+4d)
S2 = 2/2 (2a+d)
The sum of the last 3 is S5-S2, so we have
S2 = 55-48 = 7 = 2a+d
2a+d = 7
5/2 (2a+4d) = 55
a=1, d=5
So, S3 = 3/2 (2+2*5) = 18
S2 = 2/2 (2a+d)
The sum of the last 3 is S5-S2, so we have
S2 = 55-48 = 7 = 2a+d
2a+d = 7
5/2 (2a+4d) = 55
a=1, d=5
So, S3 = 3/2 (2+2*5) = 18
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.