\[y = f(x);\ \ \ y = g(x);\ \ \]
\[где\ \ f(x) = x^{2};\ \ \ g(x) = 3x^{2}\]
\[f(2x + 3) = g(x + 2)\]
\[f(2x + 3) = (2x + 3)^{2}\]
\[g(x + 2) = 3 \cdot (x + 2)^{2}\]
\[(2x + 3)^{2} = 3 \cdot (x + 2)^{2}\]
\[x² - 3 = 0\]
\[x^{2} = 3\]
\[x = \pm \sqrt{3}\]
\[Ответ:\ \pm \sqrt{3}.\]