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Find the value of the coefficient of x^4 in the expansion of (x - 2)^6.

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Question: Find the value of the coefficient of x^4 in the expansion of (x - 2)^6.

Options:

  1. 15
  2. 20
  3. 30
  4. 40

Correct Answer: 30

Solution:

Using the binomial theorem, the coefficient of x^4 in (a + b)^n is given by nCk * a^(n-k) * b^k. Here, n=6, a=x, b=-2, and k=2. Thus, the coefficient is 6C2 * (1)^4 * (-2)^2 = 15 * 4 = 60.

Find the value of the coefficient of x^4 in the expansion of (x - 2)^6.

Practice Questions

Q1
Find the value of the coefficient of x^4 in the expansion of (x - 2)^6.
  1. 15
  2. 20
  3. 30
  4. 40

Questions & Step-by-Step Solutions

Find the value of the coefficient of x^4 in the expansion of (x - 2)^6.
  • Step 1: Identify the expression we need to expand, which is (x - 2)^6.
  • Step 2: Recognize that we will use the binomial theorem to find the coefficient of x^4.
  • Step 3: In the binomial theorem, the general term in the expansion of (a + b)^n is given by nCk * a^(n-k) * b^k.
  • Step 4: Here, n = 6, a = x, and b = -2.
  • Step 5: We want the coefficient of x^4, which means we need to find the term where the power of x is 4.
  • Step 6: To find this term, we set n - k = 4, which means k = 6 - 4 = 2.
  • Step 7: Now we can calculate the coefficient using k = 2: it will be 6C2 * (x)^(6-2) * (-2)^2.
  • Step 8: Calculate 6C2, which is the number of ways to choose 2 items from 6, and it equals 15.
  • Step 9: Calculate (x)^(6-2) = (x)^4, which is just x^4.
  • Step 10: Calculate (-2)^2, which equals 4.
  • Step 11: Now combine these results: the coefficient is 15 * 1 * 4 = 60.
  • Binomial Theorem – The binomial theorem provides a formula for expanding expressions of the form (a + b)^n, where the coefficients can be calculated using combinations.
  • Coefficient Extraction – Identifying the specific coefficient of a term in a polynomial expansion, particularly focusing on the powers of x.
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