\[y = 2x^{2}\]
\[y = 800:\]
\[2x^{2} = 800\]
\[x^{2} = 400\]
\[x = - 20 \rightarrow y = 800;\]
\[x = 20 \rightarrow y = 800\]
\[Ответ:( - 20;800);(20;800).\]