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MathsMediumAssertion Reasoning2008 · Unknown

Q77.Statement-1: ∑nr=0(r + 1)nCr = (n + 2)2n−1 Statement -2: ∑nr=0(r + 1)nCrxr = (1 + x)n + nx(1 + x)n−1 . JEE Main 2008 JEE Main Previous Year Paper (1) Statement −1 is false, Statement −2 is true (2) Statement −1 is true, Statement −2 is true, Statement −2 is a correct explanation for Statement −1 (3) Statement −1 is true, Statement −2 is true; (4) Statement −1 is true, Statement −2 is false. Statement −2 is not a correct explanation for Statement −1.

What This Question Tests

This question tests the understanding of properties of binomial coefficients and the ability to derive sums using differentiation of binomial series. Statement 2 is a more general identity from which Statement 1 can be derived by setting x=1, making Statement 2 a correct explanation for Statement 1.

Concepts Tested

Sum of binomial coefficientsDifferentiation of binomial seriesGeneral term of binomial expansion

Formulas Used

∑ nCr = 2^n

∑ r nCr = n * 2^(n-1)

d/dx (1+x)^n = n(1+x)^(n-1)

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