\[y = - 2x^{2}\]
\[y = 40x:\]
\[- 2x^{2} = 40x\]
\[- 2x^{2} - 40x = 0\]
\[- 2x(x + 20) = 0\]
\[x = 0;\ \ \ x = - 20.\]
\[Ответ:(0;0);\ \ ( - 20;\ - 800).\]