In the expansion of (x + 1/x)^6, what is the coefficient of x^0?

Practice Questions

Q1
In the expansion of (x + 1/x)^6, what is the coefficient of x^0?
  1. 6
  2. 15
  3. 20
  4. 30

Questions & Step-by-Step Solutions

In the expansion of (x + 1/x)^6, what is the coefficient of x^0?
  • Step 1: Understand that (x + 1/x)^6 means we are expanding the expression (x + 1/x) raised to the power of 6.
  • Step 2: Recognize that in the expansion, we will have terms that include different powers of x.
  • Step 3: We want to find the coefficient of x^0, which means we need the term where x cancels out completely.
  • Step 4: In the expansion, each term can be represented as (x^k) * (1/x)^(6-k) for k = 0 to 6.
  • Step 5: To find x^0, we need k such that k - (6 - k) = 0, which simplifies to 2k - 6 = 0.
  • Step 6: Solving 2k - 6 = 0 gives k = 3.
  • Step 7: The term corresponding to k = 3 is (x^3) * (1/x)^(3) = x^0.
  • Step 8: The coefficient of this term can be found using the binomial coefficient, which is 6C3.
  • Step 9: Calculate 6C3, which is equal to 6! / (3! * (6-3)!) = 20.
  • Step 10: Therefore, the coefficient of x^0 in the expansion is 20.
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