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+1 vote
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in Combinatorics and Mathematical Induction by (46.9k points)
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If nC12 = nC9 find 21Cn.

1 Answer

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Best answer

nCx = nCy ⇒ x = y or x + y = n 

Here nC12 = nC9 ⇒ 12 ≠ 9 so 12 + 9 = n (i.e) n = 21

21Cn = 21C21 = 1 [nCn  = 1] 

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