# Write the sum −3+5−7+9−11+13 using sigma notation. The form of your answer will depend on your choice of the lower limit of summation.?

help pls tryna get a degree.

### 2 Answers

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- Geeganage WLv 54 weeks ago
General term of the series can be expressed as (2r+1)*(-1)^r.

Summation = r form 1 to 6, ∑(2r+1)(-1)^r

- 4 weeks ago
-3 = (-1)^1 * (1 + 1 * 2)

5 = (-1)^2 * (1 + 2 * 2)

-7 = (-1)^3 * (1 + 3 * 2)

9 = (-1)^4 * (1 + 4 * 2)

-11 = (-1)^5 * (1 + 5 * 2)

13 = (-1)^6 * (1 + 6 * 2)

See a pattern? k = 0, let the function equal (-1)^k * (1 + 2k), let the last term be 6

Or from top-down

6

(1 + 2k) * (-1)^k

0

so it is not 0 to 6 , probably just a typo

it is 1 to 6

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They want k , so remember not use r in your answer.