In the expansion of (2 + 3x)^4, what is the coefficient of x^2?

Practice Questions

Q1
In the expansion of (2 + 3x)^4, what is the coefficient of x^2?
  1. 36
  2. 54
  3. 72
  4. 90

Questions & Step-by-Step Solutions

In the expansion of (2 + 3x)^4, what is the coefficient of x^2?
  • Step 1: Identify the expression to expand, which is (2 + 3x)^4.
  • Step 2: Recognize that we need to find the coefficient of x^2 in the 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 = 2, b = 3x, and n = 4.
  • Step 5: We want the term where x has the power of 2, which means we need k = 2 (since (3x)^2 gives us x^2).
  • Step 6: Calculate C(4, 2), which is the number of ways to choose 2 from 4. C(4, 2) = 4! / (2! * (4-2)!) = 6.
  • Step 7: Calculate (2)^(4-2) = (2)^2 = 4.
  • Step 8: Calculate (3)^2 = 9.
  • Step 9: Multiply these values together: Coefficient = C(4, 2) * (2)^2 * (3)^2 = 6 * 4 * 9.
  • Step 10: Perform the multiplication: 6 * 4 = 24, then 24 * 9 = 216.
  • Step 11: Conclude that the coefficient of x^2 in the expansion of (2 + 3x)^4 is 216.
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