Easy MCQ +4 / -1

The middle term in the expansion of (x + 1/x)^(2n) is:

  1. A C(2n, n) Correct answer
  2. B C(2n, n-1)
  3. C 2 × C(2n, n)
  4. D C(2n, n) / x^n

Solution

(x+1/x)^(2n) has (2n+1) terms. Middle term = term (n+1) = C(2n,n) x^(2n-2n)/x^n = C(2n,n). Wait: T(r+1) = C(2n,r) x^(2n-r) (1/x)^r = C(2n,r) x^(2n-2r). For r=n: C(2n,n) x^(2n-2n) = C(2n,n). So middle term is C(2n,n) (constant).

About this question

Subject: Mathematics · Chapter: Binomial Theorem · Topic: Middle Term

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