SOLUTION: So I understand how summation and series sequences work but I came across a homework problem that stumped me. I can generally write a sum in summation notation really quickly but I

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Question 812881: So I understand how summation and series sequences work but I came across a homework problem that stumped me. I can generally write a sum in summation notation really quickly but I need help with the following.
Write each sum in summation notation: 1-2+3-4+...+(-50)
I get that x=1 goes under the sigma notation and 50 goes above it but I am not able to figure out what the formula is. If you could help me I would greatly appreciate it. Thank You

Found 2 solutions by htmentor, ewatrrr:
Answer by htmentor(1343)   (Show Source): You can put this solution on YOUR website!
This series consists of consecutive integers, but the sign alternates.
-1 raised to an even power is +1 and -1 raised to an odd power is -1. So the following summation notation will reproduce the given series:

Check:
The 1st term is
The 2nd term is
and so on...

Answer by ewatrrr(24785)   (Show Source): You can put this solution on YOUR website!
 
Hi
Write each sum in summation notation: 1-2+3-4+...+(-50)
When dealing with alternating + and - numbers, often used

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