Find the coefficient of x^3 in the expansion of (x - 2)^5.

Practice Questions

Q1
Find the coefficient of x^3 in the expansion of (x - 2)^5.
  1. -40
  2. -80
  3. -60
  4. -100

Questions & Step-by-Step Solutions

Find 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: Recognize that we want to find 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 x is raised to the power of 3, which means we need k = 2 (since n - k = 3).
  • Step 6: Calculate C(5, 2), which is the number of ways to choose 2 from 5. C(5, 2) = 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.
  • Binomial Expansion – The process of expanding expressions of the form (a + b)^n using the binomial theorem.
  • Coefficients in Binomial Expansion – Understanding how to find specific coefficients in the expansion using combinations.
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