# Don't ask me for extra details

Algebra Level 5

Comprehension :- If $$r^{th}$$ term of a series can be written as $$a_r = f(r)-f(r-1)$$ ,then $$S_n= \sum_{r=0}^n a_r =f(n)-f(0)$$ and $$S_\infty =\lim\limits_{n \to \infty} S_n,$$then answer the question

If $$3(3!)+4(4!)+5(5!)+...50$$ $$terms$$ $$=a!-b$$ then $$a-b$$ is equal to..

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