In the expansion of (2x - 3)^4, what is the coefficient of x^3? (2023)

Practice Questions

Q1
In the expansion of (2x - 3)^4, what is the coefficient of x^3? (2023)
  1. -108
  2. -72
  3. 72
  4. 108

Questions & Step-by-Step Solutions

In the expansion of (2x - 3)^4, what is the coefficient of x^3? (2023)
  • Step 1: Identify the expression we need to expand, which is (2x - 3)^4.
  • Step 2: Recognize that we need to find the coefficient of x^3 in this expansion.
  • Step 3: Use the Binomial Theorem, which states that (a + b)^n = Σ (nCk * a^(n-k) * b^k) for k = 0 to n.
  • Step 4: In our case, a = 2x, b = -3, and n = 4.
  • Step 5: We want the term where the power of x is 3, which means we need to find the term where k = 1 (since 4 - k = 3).
  • Step 6: Calculate the binomial coefficient for k = 1: 4C1 = 4.
  • Step 7: Calculate (2x)^(4-1) = (2x)^3 = 2^3 * x^3 = 8x^3.
  • Step 8: Calculate (-3)^1 = -3.
  • Step 9: Multiply the results from Step 6, Step 7, and Step 8: 4 * 8 * (-3).
  • Step 10: Perform the multiplication: 4 * 8 = 32, then 32 * (-3) = -96.
  • Step 11: Conclude that the coefficient of x^3 in the expansion of (2x - 3)^4 is -96.
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