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If a_n=n(n!) , then what is a₁+a₂+a₃+ +a₁₀ equal to?

Options

  1. A10!-1
  2. B11!+1
  3. C10!+1
  4. D11!-1

Correct answer

D. 11!-1

Step-by-step solution

aligned & a_n=n(n!)=(n+1) n!-n! & =(n+1)!-n! aligned Now a₁=2 ! -1 ! aligned & a₂=3!-2! & a₃=4!-3! aligned a₁₀ =11!- 10! Adding all above equations we get a₁+a₂+a₃ .+a₁₀=11!-1!

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