[Math] Find the coefficient of $x^3y^2z^3w$ in the expansion of $(2x+3y-4z+w)^9$

multinomial-coefficients

Find the coefficient of $x^3y^2z^3w$ in the expansion of $(2x+3y-4z+w)^9$

Using the formula of multinational coefficients
$$
\begin{pmatrix}
n \\
r_1,r_2,…,r_k \\
\end{pmatrix}= \ \frac{n!}{r_1! \cdot r_2! \cdot \ldots \cdot r_k!} \
$$

$$\Rightarrow \begin{pmatrix}
9 \\
3, 2, 3, 1 \\
\end{pmatrix}= \frac {9!}{3!2!3!1! } = \bbox[yellow]{5040} $$

Would the above be the answer or does one have to take this one step further by further expanding?

$$ 5040 *(2)(3)(-4)(1) = -120960$$

Best Answer

$5040 \times 2^3 \times 3^2 \times (-4)^3 \times 1 =-23224320$