\[y = 3 \bullet (x - 2)^{2}\]
\[x_{1} < x_{2} \leq 2\]
\[y_{1} - y_{2} =\]
\[= 3 \bullet \left( x_{1} - 2 \right)^{2} - 3 \bullet \left( x_{2} - 2 \right)^{2} =\]
\[= 3 \bullet \left( \left( x_{1} - 2 \right)^{2} - \left( x_{2} - 2 \right)^{2} \right) =\]
\[y_{1} - y_{2} > 0\ \Longrightarrow y_{1} > y_{2} \Longrightarrow y =\]
\[= 3 \bullet (x - 2)^{2}\ убывает\ на\ \]
\[( - \infty;2\rbrack.\]