\[ \begin{array}{l} \text{2} \quad R_3 \\ x^3 + y^3 + z^3 - 3xyz \\ (x+y)^3 + (x-z)^2 + (y-z)^2 \\ \\ \text{3} \quad R_3 \\ \frac{x^3 - 7x - 6}{x^2(x-3)^2} + 4x(3-x)^2 + 4(y-z)^2 \end{array} \]

----- Nội dung ảnh -----
\[
\begin{array}{l}
\text{2} \quad R_3 \\
x^3 + y^3 + z^3 - 3xyz \\
(x+y)^3 + (x-z)^2 + (y-z)^2 \\
\\
\text{3} \quad R_3 \\
\frac{x^3 - 7x - 6}{x^2(x-3)^2} + 4x(3-x)^2 + 4(y-z)^2
\end{array}
\]