\[y = x^{2} - 8x + 13 =\]
\[= x^{2} - 8x + 16 - 3 =\]
\[= (x - 4)^{2} - 3;\]
\[a = 1 > 0;ветви\ вверх;\]
\[x_{0} = - \frac{b}{2a} = \frac{8}{2} = 4;\]
\[y_{0} = 16 - 32 + 13 = - 3;\]
\[(4; - 3) - вершина.\]
\[При\ y = 2:\]
\[x = 1,8;\ \ x = 6,2.\]