Đáp án:
$\begin{array}{l}
a){\left( {5x - 2} \right)^2} - {\left( {6x + 1} \right)^2} + 11{x^2}\\
= 25{x^2} - 20x + 4 - \left( {36{x^2} + 12x + 1} \right) + 11{x^2}\\
= - 32x + 3\\
b)4x\left( {x - 3} \right) + 2\left( {2x - 1} \right)\left( {2x + 1} \right)\\
- 8x\left( {x - 3} \right)\\
= 4{x^2} - 12x + 2\left( {4{x^2} - 1} \right) - 8{x^2} + 24x\\
= 4{x^2} + 12x - 2\\
c)\left( {x - 7} \right)\left( {x + 7} \right) - {\left( {2x + 1} \right)^2} + 3x\left( {x + 2} \right)\\
= {x^2} - 49 - \left( {4{x^2} + 4x + 1} \right) + 3{x^2} + 6x\\
= {x^2} - 49 - 4{x^2} - 4x - 1 + 3{x^2} + 6x\\
= 2x - 50\\
d)3\left( {4 - 3x} \right)\left( {4 + 3x} \right) + {\left( {x - 2} \right)^2} + 17x\left( {x - 6} \right)\\
= 3\left( {16 - 9{x^2}} \right) + {x^2} - 4x + 4 + 17{x^2} - 102x\\
= 48 - 27{x^2} + 18{x^2} - 106x + 4\\
= - 9{x^2} - 106x + 52
\end{array}$
