Đáp án:
$\begin{array}{l}
a)2{x^2} - 7xy + x + 3{y^2} - 3y\\
= 2{x^2} - 7xy + 3{y^2} + x - 3y\\
= 2{x^2} - 6xy - xy + 3{y^2} + x - 3y\\
= 2x\left( {x - 3y} \right) - y\left( {x - 3y} \right) + x - 3y\\
= \left( {x - 3y} \right)\left( {2x - y + 1} \right)\\
b)6{x^2} - xy - 2{y^2} + 3x - 2y\\
= 6{x^2} - 4xy + 3xy - 2{y^2} + 3x - 2y\\
= 2x\left( {3x - 2y} \right) + y\left( {3x - 2y} \right) + 3x - 2y\\
= \left( {3x - 2y} \right)\left( {2x + y + 1} \right)
\end{array}$