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Question: The sum of the coefficients in the expension of (1 + 2x + 3x<sup>2</sup> +……..nx<sup>n</sup>)<sup>2...

The sum of the coefficients in the expension of

(1 + 2x + 3x2 +……..nxn)2 is –

A

Σ1

B

Sn

C

Sn2

D

Sn3

Answer

Sn3

Explanation

Solution

For sum of coefficients, Put x = 1 ;

(1 + 2 + 3 +……..n)2

= (n(n+1)2)2\left( \frac{n(n + 1)}{2} \right)^{2}

= Sn3