Đáp án:
$\begin{array}{l}
c)\\
\left( {3x + 2} \right)\left( {9{x^2} - 6x + 4} \right)\\
+ \left( {5 - 3x} \right)\left( {25 + 15x + 9{x^2}} \right) - 9\\
= 27{x^3} + 8 + 125 - 27{x^3} - 9\\
= 124\\
f){\left( {x - 3y} \right)^3} - \left( {2x - y} \right)\left( {3x + 2y} \right)\left( {3x - 2y} \right)\\
= {x^3} - 9{x^2}y + 27x{y^2} + 27{y^3}\\
- \left( {2x - y} \right)\left( {9{x^2} - 4{y^2}} \right)\\
= {x^3} - 9{x^2}y + 27x{y^2} - 27{y^3}\\
- 18{x^3} + 8x{y^2} + 9{x^2}y - 4{y^3}\\
= - 17{x^3} + 35x{y^2} - 31{y^3}
\end{array}$