Find the coefficient of x^2 in the expansion of (2x - 3)^4.

Practice Questions

Q1
Find the coefficient of x^2 in the expansion of (2x - 3)^4.
  1. 36
  2. 48
  3. 54
  4. 72

Questions & Step-by-Step Solutions

Find the coefficient of x^2 in the expansion of (2x - 3)^4.
  • Step 1: Identify the expression we need to expand, which is (2x - 3)^4.
  • Step 2: Recall the binomial theorem, which states that (a + b)^n = sum of (nCk * a^(n-k) * b^k) for k from 0 to n.
  • Step 3: In our case, a = 2x, b = -3, and n = 4.
  • Step 4: We want to find the coefficient of x^2. This means we need to find the term where the power of x is 2.
  • Step 5: To get x^2 from (2x)^k, we need k = 2, because (2x)^2 = 4x^2.
  • Step 6: The remaining power of the binomial (2x - 3) is 4 - k = 4 - 2 = 2, so we will use (-3)^2.
  • Step 7: Calculate the binomial coefficient for k = 2, which is 4C2. This is calculated as 4! / (2!(4-2)!) = 6.
  • Step 8: Now, calculate the coefficient: 4C2 * (2)^2 * (-3)^2 = 6 * 4 * 9.
  • Step 9: Perform the multiplication: 6 * 4 = 24, and then 24 * 9 = 216.
  • Step 10: The coefficient of x^2 in the expansion of (2x - 3)^4 is 216.
  • Binomial Theorem – The binomial theorem provides a formula for expanding expressions of the form (a + b)^n, where the coefficients can be determined using combinations.
  • Coefficient Extraction – Identifying the specific coefficient of a term in a polynomial expansion, particularly focusing on the powers of the variable.
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