Question

Check if my answer is right?

Answer 1

here it is

Answer 2

\[\sum_{i=12}^{25}(-5+13i)=-5\sum_{i=12}^{25}1+13\sum_{i=12}^{25}i\]
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Think:

\[\sum_{i=k}^{n}1=1(n-k+1)=n-k+1\]
\[\sum_{i=1}^{25}i=\sum_{i=1}^{11}i+\sum_{i=12}^{25}i=\frac{25(25+1)}{2}=325\]
but
\[\sum_{i=1}^{11}i=\frac{11(11+1)}{2}=66\]
so we have
\[66+\sum_{i=12}^{25}i=325\]
=>\[\sum_{i=12}^{25}i=325-66=259\]
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so we have
\[-5\sum_{i=12}^{25}1+13\sum_{i=12}^{25}i\]
\[-5(25-12+1)+13(259)=3297\]

Answer 3

Wow, thank you, you deserve more than just 1 medal for this :O that was a lot for you to put. Thank you

Answer 4

lol
i didn't want to post something that wasn't readable

Answer 5

Haha well this was very helpful, I greatly thank you :)

Answer 6

Thanks :)

Answer 7

No problem :)