Đáp án:
$\begin{array}{l}
1)\\
\left( {3x - 1} \right)\left( {2x + 7} \right) - \left( {x + 1} \right)\left( {6x - 5} \right)\\
= 6{x^2} + 21x - 2x - 7 - \left( {6{x^2} - 5x + 6x - 5} \right)\\
= 6{x^2} + 19x - 7 - 6{x^2} - x + 5\\
= 18x - 2\\
2)\\
\left( {3x - 5} \right)\left( {7 - 5x} \right) + \left( {5x + 2} \right)\left( {3x - 2} \right) - 2\\
= 21x - 15{x^2} - 35 + 25x\\
+ 15{x^2} - 10x + 6x - 4 - 2\\
= 42x - 41\\
3)x\left( {x - \dfrac{1}{3}} \right) - \dfrac{1}{2}x\left( {2x - 3} \right)\\
= {x^2} - \dfrac{1}{3}x - {x^2} + \dfrac{3}{2}x\\
= \dfrac{3}{2}x - \dfrac{1}{3}x\\
= \dfrac{7}{6}x
\end{array}$
