Math Problem Statement

  1. What is the third term in the expansion of (x+5)^4? a. 20x^2 b. 40x^2 c. 60x^2 d. 80x^2

Solution

To find the third term in the expansion of (x+5)4(x + 5)^4, we can use the Binomial Theorem. The Binomial Theorem states that:

(a+b)n=k=0n(nk)ankbk(a + b)^n = \sum_{k=0}^{n} \binom{n}{k} a^{n-k} b^k

In this case, a=xa = x, b=5b = 5, and n=4n = 4.

The general term (k-th term) in the expansion is given by:

Tk+1=(nk)ankbkT_{k+1} = \binom{n}{k} a^{n-k} b^k

For the third term (k=2k = 2):

T3=(42)x4252T_3 = \binom{4}{2} x^{4-2} \cdot 5^2

First, calculate the binomial coefficient:

(42)=4!2!(42)!=4×32×1=6\binom{4}{2} = \frac{4!}{2!(4-2)!} = \frac{4 \times 3}{2 \times 1} = 6

Now, plug in the values:

T3=6x225=150x2T_3 = 6 \cdot x^2 \cdot 25 = 150x^2

However, the options provided do not match 150x2150x^2. There seems to be a discrepancy with the problem statement or options. Let me correct it.

Let's recalculate:

For the third term:

T3=(42)x4252=6x225=150x2T_3 = \binom{4}{2} \cdot x^{4-2} \cdot 5^2 = 6 \cdot x^2 \cdot 25 = 150x^2

If the problem had a mistake in options, the correct coefficient would be 150x^2.

But if using different coefficients, we'd find the correct answer should be based on the corrected interpretation or problem. Given the process, none match perfectly. No provided option (a-d) matches this outcome.

You should verify the problem's coefficients or choices.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Binomial Expansion
Algebra

Formulas

Binomial Theorem: (a + b)^n = ∑(k=0 to n) (n choose k) * a^(n-k) * b^k
General term: T(k+1) = (n choose k) * a^(n-k) * b^k

Theorems

Binomial Theorem

Suitable Grade Level

Grades 9-12