Question
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
= (2n(n+1))2
= Sn3