If - r -1 n r -55-find - r -1 n r 3

We have, ∑^n_r 1r=55 ⇒n(n+1)/2=55 ...(i) Now, ∑^n_r 1r^3= [ n(n+1)/2 ]^2 =[55]^2 [Using equation (i),we get] =3025 ...

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If ∑ r -1 n r...

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If $\sum_{r - 1}^{n} r = 55$ ,find $\sum_{r - 1}^{n} r^{3}$

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\sum_{r = 1}^{n} r = 55, find \sum_{r = 1}^{n} r^{3}

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