Đáp án:
$\begin{array}{l}
a)5x\left( {12 - 5x} \right) - \left( {6x - 3} \right)\left( {5 - 4x} \right)\\
= 60x - 25{x^2} - 30x + 24{x^2} + 15 - 12x\\
= - {x^2} + 18x + 15\\
b){\left( {5 - 2x} \right)^2} + 5x\left( {x - 1} \right) - {\left( {1 - 3x} \right)^2}\\
= 25 - 20x + 4{x^2} + 5{x^2} - 5x - 1 + 6x - 9{x^2}\\
= - 19x + 24\\
c){\left( {2x - 1} \right)^3} - 8\left( {x - 3} \right)\left( {3 + x} \right) + 12x\left( {x - 2} \right)\\
= 8{x^3} - 12{x^2} + 6x - 1 - 8\left( {9 - {x^2}} \right) + 12{x^2} - 24x\\
= 8{x^3} + 8{x^2} - 18x - 73\\
d){\left( {2x - 7} \right)^2} - 3{\left( {x - 1} \right)^2} + \left( {x + 6} \right)\left( {6 - x} \right)\\
= 4{x^2} - 28x + 49 - 3{x^2} + 6x - 3 + 36 - {x^2}\\
= - 22x + 82
\end{array}$
