In the expansion of (x + 2)^7, what is the term containing x^5?

Practice Questions

Q1
In the expansion of (x + 2)^7, what is the term containing x^5?
  1. 672
  2. 6720
  3. 67200
  4. 672000

Questions & Step-by-Step Solutions

In the expansion of (x + 2)^7, what is the term containing x^5?
  • Step 1: Identify the expression we are expanding, which is (x + 2)^7.
  • Step 2: Use the Binomial Theorem, which states that (a + b)^n = Σ (nCk * a^(n-k) * b^k) for k = 0 to n.
  • Step 3: In our case, a = x, b = 2, and n = 7.
  • Step 4: We want the term that contains x^5. This means we need to find k such that n - k = 5.
  • Step 5: Solve for k: 7 - k = 5, which gives k = 2.
  • Step 6: Now, we can find the term using k = 2: The term is given by 7C2 * (x)^(7-2) * (2)^2.
  • Step 7: Calculate 7C2, which is 7! / (2! * (7-2)!) = 21.
  • Step 8: Calculate (2)^2, which is 4.
  • Step 9: Combine these results: The term is 21 * 4 * x^5.
  • Step 10: Multiply 21 and 4 to get 84, so the term is 84x^5.
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