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AP EAMCET · Maths · Binomial Theorem

What is the sum of the first \(n\)-terms of the series, whose \(k\)-term is \(k ! \times k\) ?

  1. A \((n+1) !^n-1\)
  2. B \((n+1)^n-1\)
  3. C \((n+1) !-1\)
  4. D \(3 n-2\)
Verified Solution

Answer & Solution

Correct Answer

(C) \((n+1) !-1\)

Step-by-step Solution

Detailed explanation

Given, \(\begin{aligned} t_k & =k k !=(k+1-1) k ! \\ & =(k+1) k !-k !=(k+1) !-k !\end{aligned}\) \(\begin{aligned} & t_1=2 !-1 ! \\ & t_2=3 !-2 ! \\ & t_3=4 !-3 !\end{aligned}\) ......... ......... \(\underline{t_n=(n+1) !-n !}\) \(t_1+t_2+\ldots .+t_n=(n+1) !-1\) \(\therefore\)…