Giải thích các bước giải:
\(\begin{array}{l}
a)\, = \left( {6{x^5}{y^2}:3{x^3}{y^2}} \right) - \left( {9{x^4}{y^3}:3{x^3}{y^2}} \right) + \left( {15{x^3}{y^4}:3{x^3}{y^2}} \right)\\
= 2{x^2} - 3{x^2}y + 5{y^2}\\
b)\, = \left( {2{x^3} - 10{x^2} - 11{x^2} + 55x + 12x - 60} \right):\left( {x - 5} \right)\\
= \left( {2{x^2}\left( {x - 5} \right) - 11x\left( {x - 5} \right) + 12\left( {x - 5} \right)} \right):\left( {x - 5} \right)\\
= \left( {2{x^2} - 11x + 12} \right)\left( {x - 5} \right):\left( {x - 5} \right)\\
= 2{x^2} - 11x + 12
\end{array}\)
