JEE Advance - Mathematics (1983 - No. 1)
The unit vector perpendicular to the plane determined by $$P\left( {1, - 1,2} \right),\,Q\left( {2,0, - 1} \right)$$ and $$R\left( {0,2,1} \right)$$ is ...........
{{2\widehat i + \widehat j + \widehat k} \over {\sqrt 6 }}
{{-2\widehat i - \widehat j - \widehat k} \over {\sqrt 6 }}
{{2\widehat i + \widehat j + \widehat k} \over {\sqrt 3 }}
{{-2\widehat i - \widehat j - \widehat k} \over {\sqrt 3 }}
\pm {{2\widehat i + \widehat j + \widehat k} \over {\sqrt 6 }}