Find SUM_(k=10)^15 tk for an arithmetic sequence with 10th term being -10 and 20th term being 15, where tk represents the kth term of this arithmetic sequence.© BrainMass Inc. brainmass.com October 10, 2019, 12:55 am ad1c9bdddf
If we consider a as the first term of the given arithmetic sequence, and d as the common difference, then kth term will be obtained by adding (k-1) differences to the first term, i.e.
tk = a + (k-1)d
Thus, we can generate following equations.
t10 = a + (10-1)d = ...
Solution shows two different approaches to compute the required sum.