Mathematics · supplementary
Second weighted sum of coefficients for JEE
Binomial theorem for a positive integral index
Formula
\[\sum_{r=0}^{n}r(r-1){n\choose r}=n(n-1)2^{n-2}\]
Variables: \(n\) is a positive integer.
Finding \(\sum r^2{n\choose r}\), advanced coefficient-sum questions.