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B
3
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C
−3
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D
4
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Solution
The correct option is B3 (n+1)!=12×(n−1)!⇒(n+1)n(n−1)!=12×(n−1)!⇒n2+n=12(∵n−1≠0)⇒n2+n−12=0⇒(n+4)(n−3)=0⇒n=−4,3 ∵n=−4 does not satisfy the given equation. ∴n=3,(∵n∈N)