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प्रश्न
Find n, if `(1!)/("n"!) = (1!)/(4!) - 4/(5!)`
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उत्तर
`(1!)/("n"!) = (1!)/(4!) - 4/(5!)`
∴ `(1!)/("n"!) = (1!)/(4!) - 4/(5 xx 4!)`
∴ `(1!)/("n"!) = (1!)/(4!)[1 - 4/5]`
∴ `(1!)/("n"!) = (1!)/(4!)[(5 - 4)/5]`
∴ `1/("n"!) = 1/(4!) xx 1/5`
∴ `1/("n"!) = 1/(5!)`
∴ n! = 5!
∴ n = 5
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