Find the following sum
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Find the following sum

[From: ] [author: ] [Date: 11-06-08] [Hit: ]
(2 - 6n) = -4, so a(1) = -4 and a(n) = (2 - 6n)Thus there are n many numbers in this sequence.Add the first number to the last number, multiply by the number of number , and divide by 2........
-4-10-16+...+(2-6n)

The answer may be a function of n.

Help please

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The answer is a function of n. Let us assume that (2 - 6n) is the last member of the sequence.

Since you are constantly subtracting six, we have to determine how many numbers are in this sequence.

For n = 1, (2 - 6n) = -4, so a(1) = -4 and a(n) = (2 - 6n) Thus there are n many numbers in this sequence.

Add the first number to the last number, multiply by the number of number , and divide by 2.

(((-4 + 2 - 6n) * n) / 2) = (-2n - 6n^2) / 2 = (-3n^2 - n) <----- Answer

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