Đáp án: $A = \dfrac{5}{{229}}$
Giải thích các bước giải:
$\begin{array}{l}
A = \dfrac{3}{{229}}.\left( {2 + \dfrac{1}{{433}}} \right) - \dfrac{1}{{229}}.\dfrac{{432}}{{433}} - \dfrac{4}{{229.443}}\\
= \dfrac{3}{{229}}.\dfrac{{867}}{{433}} - \dfrac{{432}}{{229.433}} - \dfrac{4}{{229.433}}\\
= \dfrac{1}{{229.433}}.\left( {3.867 - 432 - 4} \right)\\
= \dfrac{1}{{229.433}}.2165\\
= \dfrac{5}{{229}}
\end{array}$