The problem asks us to find the coefficient of the $y^3$ term in the binomial expansion of $(x - 2y)^4$.

AlgebraBinomial TheoremPolynomial ExpansionCoefficients
2025/4/5

1. Problem Description

The problem asks us to find the coefficient of the y3y^3 term in the binomial expansion of (x2y)4(x - 2y)^4.

2. Solution Steps

We can use the binomial theorem to find the coefficient. 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 our case, we have (x2y)4(x - 2y)^4. We want to find the term with y3y^3, so we need to find the term where k=3k = 3.
Here, a=xa = x, b=2yb = -2y, and n=4n = 4.
So we have:
(43)x43(2y)3\binom{4}{3} x^{4-3} (-2y)^3
(43)=4!3!(43)!=4!3!1!=4×3×2×1(3×2×1)(1)=4\binom{4}{3} = \frac{4!}{3!(4-3)!} = \frac{4!}{3!1!} = \frac{4 \times 3 \times 2 \times 1}{(3 \times 2 \times 1)(1)} = 4
Now, we plug in the values:
4x1(2y)3=4x(8y3)=32xy34 \cdot x^{1} \cdot (-2y)^3 = 4 \cdot x \cdot (-8y^3) = -32xy^3
The coefficient of y3y^3 is 32x-32x. However, we are looking for the coefficient of the y3y^3 term, meaning we want the value that y3y^3 is multiplied by.
The term with y3y^3 is given by:
(43)x43(2y)3=(43)x1(2y)3=4x(8y3)=32xy3\binom{4}{3}x^{4-3}(-2y)^3 = \binom{4}{3}x^1(-2y)^3 = 4x(-8y^3) = -32xy^3.
So, the coefficient of y3y^3 in the binomial expansion of (x2y)4(x - 2y)^4 is 32x-32x. However, the prompt is slightly ambiguous, but given the answer format used in the question, it is most likely asking for the numerical coefficient of the xy3xy^3 term. Therefore we consider the term 32xy3-32xy^3 and observe that the coefficient of xy3xy^3 is -
3
2.

3. Final Answer

-32