\[\boxed{\text{146.}\text{\ }\text{ОК\ ГДЗ\ -\ домашка\ на\ 5}}\]
\[f(x) = ax^{2} - b\]
\[b = - 4;\ \ A(3;0)\]
\[0 = 9a - 4\]
\[9a = 4\]
\[a = \frac{4}{9}.\]
\[f(x) = \frac{4}{9}x^{2} - 4\]
\[\frac{4}{9}x^{2} - 4 = 68\]
\[\frac{4}{9}x^{2} = 72\]
\[x^{2} = 72 \cdot \frac{9}{4}\]
\[x^{2} = 18 \cdot 9 = 162\]
\[x = \pm \sqrt{162} = \pm 9\sqrt{2}.\]
\[Ответ:при\ x = \pm 9\sqrt{2}\text{.\ }\]