Question:medium

If \( x + y = 1 \), then \[ \sum_{r=0}^{n} r^2 \cdot n C_r x^r y^{n-r} \quad \text{is equal to:} \]

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When solving summation problems with binomial coefficients, look for standard identities to simplify the expression.

Updated On: Apr 22, 2026

\( nxy \)
\( n x(x + y n) \)
\( n x (x + y) \)
None of these

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The Correct Option is C

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