https://media.discordapp.net/attachments/882003794098020352/935966934195929178/IMG_20220127_000815.j

[pseudo bison]

help pls

[undone fiber]

1. Wait patiently for a helper to come along.
2. Once someone helps you, say thank you and close the thread with:

+close

3. Feel free to nominate the person for helper of the week in #helper-nominations
4. Do not ping the mods, unless someone is breaking the rules.
5. If you're happy with the help you got here, and the server overall, you can contribute financially as well:

[pseudo bison]

https://media.discordapp.net/attachments/882003794098020352/935966934195929178/IMG_20220127_000815.jpg

this is the question

[gusty girder]

Note that the first sum is $$1^2(2^2+3^2+\cdots+n^2)+2^2(3^2+4^2+\cdots+n^2)+(n-1)^2 n^2$$ which can be rewritten as $$\sum^{n-1}{k=1} \left[k^2 \cdot \sum^{n}{r=k+1} r^2 \right]$$

[fervent crag]

Civil Service Pigeon

[gusty girder]

Then to find the integral, ||substitute the double angle|| then ||substitute t=sinx||, the rest is straightforward

[pseudo bison]

ok thx