If `(n+1)! =90 xx(n-1)!, ` find n. – InterviewSolution

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1.	If `(n+1)! =90 xx(n-1)!, ` find n.
Answer» We have `(n+1)! =90 xx(n-1)! ` `rArr (n+1)xxnxx(n-1)! =90xx(n-1)! ` `rArr (n+1)n=90 ` ` rArr (n+1)n=10xx9 ` [ writing 90 as product of two consecutive integers] ` rArr n=9. ` Hence, `n=9. `

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