I have to find the sum of of this sequence. Lowest bound is 2 and highest bound is 7
in Algebra 2 Answers by

Your answer

Your name to display (optional):
Privacy: Your email address will only be used for sending these notifications.
Anti-spam verification:
To avoid this verification in future, please log in or register.

1 Answer

An arithmetic sequence is of the form a, a+d, a+2d,..., a+(n-1)d.

This produces the sum na+d(1+2+..+n-1)=na+nd(n-1)/2=½(2a+nd-d)n.

This expression is a quadratic in n, so there is n no cube term, and 9-n³ could not be the sum to n terms of any arithmetic sequence.

However, if 9-n³ defines the nth term of a series (non-arithmetic), then we can calculate each term from 2 to 7:

1, -18, -55, -116, -207, -334, the sum of which is -729.

 

by Top Rated User (614k points)

Related questions

1 answer
asked Jun 20, 2013 in Algebra 2 Answers by anonymous | 107 views
Welcome to MathHomeworkAnswers.org, where students, teachers and math enthusiasts can ask and answer any math question. Get help and answers to any math problem including algebra, trigonometry, geometry, calculus, trigonometry, fractions, solving expression, simplifying expressions and more. Get answers to math questions. Help is always 100% free!
82,238 questions
86,751 answers
1,943 comments
3,650 users