What is the coefficient of x^5 in the expansion of (2x - 1)^6?

Practice Questions

Q1
What is the coefficient of x^5 in the expansion of (2x - 1)^6?
  1. 32
  2. 48
  3. 64
  4. 80

Questions & Step-by-Step Solutions

What is the coefficient of x^5 in the expansion of (2x - 1)^6?
  • Step 1: Identify the expression we need to expand, which is (2x - 1)^6.
  • Step 2: Use the Binomial Theorem, which states that (a + b)^n = sum(C(n, k) * a^(n-k) * b^k) for k from 0 to n.
  • Step 3: In our case, a = 2x, b = -1, and n = 6.
  • Step 4: We want the term that contains x^5. This occurs when we choose (2x) 5 times and (-1) 1 time.
  • Step 5: Calculate the number of ways to choose 5 from 6, which is C(6, 5). C(6, 5) = 6.
  • Step 6: Calculate (2x)^5. This is (2^5)(x^5) = 32x^5.
  • Step 7: Calculate (-1)^1, which is -1.
  • Step 8: Combine these results to find the coefficient: Coefficient = C(6, 5) * (2^5) * (-1) = 6 * 32 * (-1).
  • Step 9: Calculate 6 * 32 = 192.
  • Step 10: Multiply by -1 to get the final coefficient: -192.
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