$\begin{gathered}
  \left\{ {\begin{array}{*{20}{c}}
  {y = 2} \\ 
  {y = x} 
\end{array}\, \Rightarrow \left[ {\begin{array}{*{20}{c}}
  2 \\ 
  2 
\end{array}} \right]} \right. \hfill \\
  \left\{ {\begin{array}{*{20}{c}}
  {y = 2} \\ 
  {y + x = 10} 
\end{array} \Rightarrow \left[ {\begin{array}{*{20}{c}}
  8 \\ 
  2 
\end{array}} \right]} \right. \hfill \\ 
\end{gathered} $

$\begin{gathered}
  \underline {\left\{ {\begin{array}{*{20}{c}}
  {y = x} \\ 
  {y + x = 10} 
\end{array}} \right.}  \hfill \\
  x + x = 10 \Rightarrow x = 5 \hfill \\
  y = 5 \Rightarrow \left[ {\begin{array}{*{20}{c}}
  5 \\ 
  5 
\end{array}} \right] \hfill \\ 
\end{gathered} $

محیط مثلث محصور:

$\begin{gathered}
   = \sqrt {18}  + \sqrt {18}  + 6 \hfill \\
   = 2\sqrt {18}  + 6 = 6\sqrt 2  + 6 \hfill \\
   \Rightarrow \sqrt {18}  = \sqrt {9 \times 2}  = 3\sqrt 2  \hfill \\ 
\end{gathered} $