Giải thích các bước giải:
\(\begin{array}{l}
c.Xét:\left( {x - 2} \right) \in U\left( 5 \right)\forall x \in Z\\
\to \left[ \begin{array}{l}
x - 2 = 5\\
x - 2 = - 5\\
x - 2 = 1\\
x - 2 = - 1
\end{array} \right. \to \left[ \begin{array}{l}
x = 7\\
x = - 3\\
x = 3\\
x = 1
\end{array} \right. \to \left[ \begin{array}{l}
C = 1\\
C = - 1\\
C = 5\\
C = - 5
\end{array} \right.\\
\to Mi{n_C} = - 5 \Leftrightarrow x = 1\\
d.D = \frac{{x - 4 + 9}}{{x - 4}} = 1 + \frac{9}{{x - 4}}\\
Xét:x - 4 \in U\left( 9 \right)\\
\to \left[ \begin{array}{l}
x - 4 = 9\\
x - 4 = - 9\\
x - 4 = 3\\
x - 4 = - 3\\
x - 4 = 1\\
x - 4 = - 1
\end{array} \right. \to \left[ \begin{array}{l}
x = 13\\
x = - 5\\
x = 7\\
x = 1\\
x = 5\\
x = 3
\end{array} \right. \to \left[ \begin{array}{l}
D = 2\\
D = 0\\
D = 4\\
D = - 2\\
D = 10\\
D = - 8
\end{array} \right.\\
\to Mi{n_D} = - 8 \Leftrightarrow x = 3
\end{array}\)
