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## boomerang285 2 years ago Please help with this sigma problem, i think the answer is 10!!

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1. boomerang285

$\sum_{1}^{3} (3i+1)$

2. boomerang285

and I also have this one which is $\sum_{1}^{2} 3i$

3. boomerang285

which i think is 6???

4. hjhancock

the 1 on the bottom is giving you your starting place and the 3 on the top is telling you how many times to go through it so for the first on, you have (3*1+1)+(3*2+1)+(3*3+1)

5. boomerang285

oooohhh so its 21, that makes total sense, and I also see what I was doing wrong...

6. boomerang285

so would the answer to the second one then be 9 instead of 6?

7. hjhancock

yeah, because you iterate twice(the 2 on the top) so its (3*1)+(3*2)

8. boomerang285

gotcha, thank you so much!

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