Đáp án:
$\begin{array}{l}
a){\left( {5x + 1} \right)^2} - \left( {5x + 3} \right)\left( {5x - 3} \right)\\
= 25{x^2} + 10x + 1 - \left( {25{x^2} - 9} \right)\\
= 25{x^2} + 10x + 1 - 25{x^2} + 9\\
= 10x + 10\\
b){\left( {x + 3} \right)^2} + \left( {x - 2} \right)\left( {x + 2} \right) - 2{\left( {x - 1} \right)^2}\\
= {x^2} + 6x + 9 + {x^2} - 4 - 2\left( {{x^2} - 2x + 1} \right)\\
= 2{x^2} + 6x + 5 - 2{x^2} + 4x - 2\\
= 10x + 3
\end{array}$