What is the coefficient of x^3 in the expansion of (x - 2)^5?

Practice Questions

Q1
What is the coefficient of x^3 in the expansion of (x - 2)^5?
  1. 10
  2. 20
  3. 30
  4. 40

Questions & Step-by-Step Solutions

What is the coefficient of x^3 in the expansion of (x - 2)^5?
  • Step 1: Identify the expression we need to expand, which is (x - 2)^5.
  • Step 2: Understand that we want the coefficient of x^3 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 = -2, and n = 5.
  • Step 5: We need to find the term where the power of x is 3, which means we need k = 2 (since 5 - k = 3).
  • Step 6: Calculate C(5, 2), which is the number of ways to choose 2 from 5. This is equal to 5! / (2! * (5-2)!) = 10.
  • Step 7: Calculate (-2)^2, which is 4.
  • Step 8: Multiply the results from Step 6 and Step 7: 10 * 4 = 40.
  • Step 9: Conclude that the coefficient of x^3 in the expansion of (x - 2)^5 is 40.
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