Question

The algebric form of an arithmetic sequence is 2n-1 The sum of its first five terms is ______? please answer mee​

Answer 1

Answer:

If the n -th term of a sequence is n2+2n then it is a quadratic sequence (not an arithmetic sequence). If you know that ∑Nn=1n2=1/6N(N+1)(2N+1) and ∑Nn=1=1/2N(N+1) then break it into two sums and use those formulas.

Edit: another way: note that n2+2n=(n2+2n+1)−1=(n+1)2−1 , so you could sum that.

Answer 2

Answer:

Hope it helped you

Step-by-step explanation:

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