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Question
Find n if 2nCr–1 = 2nCr+1
Solution
2nCr–1 = 2nCr+1
We know that if nCr = nCy, then x = y or x + y = n
∴ r – 1 + r + 1 = 2n ...[∵ x = y is not possible]
∴ 2r = 2n
∴ r = n
∴ n = r.
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