If [tex]\sum^{n}_{r=1} u_r =3n^2 +4n [/tex], what is [tex] \sum^{n-1}_{r=1}u_r [/tex] ?(adsbygoogle = window.adsbygoogle || []).push({});

I know that [tex] \sum^{n-1}_{r=1}u_r [/tex] is equals to [tex]\sum^{n}_{r=1} u_r =3n^2 +4n - u_n [/tex] but the answer given is [tex] 3n^2-2n-1[/tex]. How do i express it in that way?

thanks alot.

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# Homework Help: Question regarding summation of series

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