A) $2x^2-5x+2=2x^2-4x-x+2=2x(x-2)-(x-2)$
$=(x-2)(2x-1)=0$
$\Rightarrow \left[ \begin{array}{l} x-2=0\\2x-1=0\end{array} \right .$
$\Rightarrow \left[ \begin{array}{l} x=2(tm)\\x=\dfrac{1}{2}(tm) \end{array}\right .$
$\Rightarrow A=\{2;\dfrac{1}{2}\}$