Given that $\displaystyle \sum_{r = 1}^{n}U_r=3n^2+4n$, find $\displaystyle U_n$ and $\displaystyle \sum_{r = n+1}^{2n}U_r$

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- May 21st 2011, 06:13 AMPunchFinding the general term from summation
Given that $\displaystyle \sum_{r = 1}^{n}U_r=3n^2+4n$, find $\displaystyle U_n$ and $\displaystyle \sum_{r = n+1}^{2n}U_r$

- May 21st 2011, 06:39 AMPlato
- May 21st 2011, 07:49 AMPunch
- May 21st 2011, 07:53 AMPlato
Very good.

Now what is $\displaystyle U_{2n}-U_n~?$ - May 21st 2011, 08:08 AMDuke
9n^2+4n