\[\ x² = 17\]
\[x = \pm \sqrt{17}\]
\[Ответ:x = \pm \sqrt{17}.\]
\[\text{\ \ }y \geq 0:\]
\[y^{3} \cdot \sqrt{4y^{2}} = 2y^{3|y|} = 2y^{4}.\]