In the expansion of (2x + 5)^3, what is the coefficient of x^2?

Practice Questions

Q1
In the expansion of (2x + 5)^3, what is the coefficient of x^2?
  1. 30
  2. 60
  3. 90
  4. 120

Questions & Step-by-Step Solutions

In the expansion of (2x + 5)^3, what is the coefficient of x^2?
  • Step 1: Identify the expression we are expanding, which is (2x + 5)^3.
  • Step 2: Recognize that we need to find the coefficient of x^2 in this expansion.
  • Step 3: Use the Binomial Theorem, which states that (a + b)^n = Σ (nCk * a^(n-k) * b^k) for k = 0 to n.
  • Step 4: In our case, a = 2x, b = 5, and n = 3.
  • Step 5: We want the term where x has the power of 2, which means we need to find the term where (2x) is raised to the power of 2.
  • Step 6: This corresponds to k = 1 in the Binomial Theorem because n - k = 2 (3 - 1 = 2).
  • Step 7: Calculate the binomial coefficient for k = 1, which is 3C1 = 3.
  • Step 8: Calculate (2x)^2, which is 4x^2.
  • Step 9: Calculate 5^1, which is 5.
  • Step 10: Multiply these values together: 3 (from 3C1) * 4 (from (2x)^2) * 5 (from 5^1) = 3 * 4 * 5.
  • Step 11: Perform the multiplication: 3 * 4 = 12, and then 12 * 5 = 60.
  • Step 12: Conclude that the coefficient of x^2 in the expansion of (2x + 5)^3 is 60.
No concepts available.
Soulshift Feedback ×

On a scale of 0–10, how likely are you to recommend The Soulshift Academy?

Not likely Very likely