A Partial Weighted Coefficient Sum

★ 7/10combinatorics algebra Binomial Theorem Symmetry

Problem

Let $(1+x)^{50}=a_0+a_1x+a_2x^2+\cdots+a_{50}x^{50}$ . Find the value of

a_1+2a_2+3a_3+\cdots+25a_{25}.

Answer

Solution

Difficulty	7/10
Topics	combinatorics, algebra, Binomial Theorem, Symmetry

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