What is the coefficient of x^2 in the expansion of (x + 1/2)^8?

Practice Questions

Q1
What is the coefficient of x^2 in the expansion of (x + 1/2)^8?
  1. 28
  2. 56
  3. 70
  4. 84

Questions & Step-by-Step Solutions

What is the coefficient of x^2 in the expansion of (x + 1/2)^8?
  • Step 1: Identify the expression to expand, which is (x + 1/2)^8.
  • Step 2: Understand that we need to find the coefficient of x^2 in this expansion.
  • Step 3: Use the binomial theorem, which states that (a + b)^n = Σ (C(n, k) * a^(n-k) * b^k) for k = 0 to n.
  • Step 4: In our case, a = x, b = 1/2, and n = 8.
  • Step 5: We want the term where x is raised to the power of 2, which means we need k = 2.
  • Step 6: Calculate C(8, 2), which is the number of ways to choose 2 items from 8. This is calculated as 8! / (2!(8-2)!) = 28.
  • Step 7: Calculate (1/2)^2, which is 1/4.
  • Step 8: Multiply the results from Step 6 and Step 7: 28 * (1/4) = 7.
  • Step 9: Conclude that the coefficient of x^2 in the expansion of (x + 1/2)^8 is 7.
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