\[\boxed{\mathbf{119}\mathbf{.}}\]
\[y = \frac{3}{8}x^{4} - x^{3} + 2;\]
\[D(f) = R;\]
\[y^{'} = \frac{3}{8} \cdot 4x^{3} - 3x^{2} = \frac{3}{2}x^{3} - 3x^{2};\]
\[y^{''} = \frac{3}{2} \cdot 3x^{2} - 6x = \frac{9}{2}x^{2} - 6x;\]
\[\frac{9}{2}x^{2} - 6x = 0\]
\[\frac{9}{2}x\left( x - \frac{4}{3} \right) = 0\]
\[x = 0;\ \ x = \frac{4}{3}.\]
\[Ответ:\ x = 0;\ \ x = \frac{4}{3}.\]