What is the coefficient of x^2 in the expansion of (2x + 1)^6?

Practice Questions

Q1
What is the coefficient of x^2 in the expansion of (2x + 1)^6?
  1. 15
  2. 30
  3. 45
  4. 60

Questions & Step-by-Step Solutions

What is the coefficient of x^2 in the expansion of (2x + 1)^6?
  • Step 1: Identify the expression to expand, which is (2x + 1)^6.
  • Step 2: Recognize 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 = 2x, b = 1, and n = 6.
  • Step 5: We want the term where x has the power of 2, which means we need to find the term where (2x) is raised to the power of 2.
  • Step 6: This corresponds to k = 4 because n - k = 2 (6 - k = 2). So, k = 4.
  • Step 7: Calculate C(6, 4), which is the number of ways to choose 4 from 6. C(6, 4) = 15.
  • Step 8: Calculate (2)^2, which is 4.
  • Step 9: Calculate (1)^4, which is 1.
  • Step 10: Multiply these values together: C(6, 4) * (2)^2 * (1)^4 = 15 * 4 * 1 = 60.
  • Step 11: The coefficient of x^2 in the expansion of (2x + 1)^6 is 60.
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