If omega is a complex cube root of unity,then | vedclass

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(C) We have,$\sum_{r=1}^{n-1} r(r+1-\omega)(r+1-\omega^2)$ $= \sum_{r=1}^{n-1} r((r+1)^2 - (r+1)(\omega + \omega^2) + \omega^3)$ Since $\omega^3 = 1$

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$\frac{n(n-1)}{4}(n^2+3n+4)$

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(C) We have,$\sum_{r=1}^{n-1} r(r+1-\omega)(r+1-\omega^2)$ $= \sum_{r=1}^{n-1} r((r+1)^2 - (r+1)(\omega + \omega^2) + \omega^3)$ Since $\omega^3 = 1$ and $1 + \omega + \omega^2 = 0$,we have $\omega + \omega^2 = -1$. $= \sum_{r=1}^{n-1} r((r+1)^2 + (r+1) + 1)$ $= \sum_{r=1}^{n-1} r(r^2 + 2r + 1 + r + 1 + 1) = \sum_{r=1}^{n-1} r(r^2 + 3r + 3)$ $= \sum_{r=1}^{n-1} (r^3 + 3r^2 + 3r)$ $= \left[\frac{(n-1)n}{2}\right]^2 + 3 \cdot \frac{(n-1)n(2n-2+1)}{6} + 3 \cdot \frac{(n-1)n}{2}$ $= \frac{n^2(n-1)^2}{4} + \frac{n(n-1)(2n-1)}{2} + \frac{3n(n-1)}{2}$ $= \frac{n(n-1)}{4} [n(n-1) + 2(2n-1) + 6]$ $= \frac{n(n-1)}{4} [n^2 - n + 4n - 2 + 6]$ $= \frac{n(n-1)}{4} (n^2 + 3n + 4)$

If $\omega$ is a complex cube root of unity,then for any $n>1$,$\sum_{r=1}^{n-1} r(r+1-\omega)(r+1-\omega^2) =$

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