\[\boxed{\mathbf{517\ (517).\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[1)\ y = \sqrt{x^{2}} - 2x,\ \ x \geq 0\]
\[y = |x| - 2x\]
\[y = x - 2x\]
\[y = - x\]
\[2)\ y = \sqrt{- x} \cdot \sqrt{- x}\]
\[y = \sqrt{x^{2}}\]
\[y = |x|\]
\[y = \left\{ \begin{matrix} x,\ \ x \geq 0 \\ - x,\ \ x < 0 \\ \end{matrix} \right.\ \ \]