Find a unit vector perpendicular to the plane determined by the points `(1,-1,2),(2,0,-1)a n d(0,2,1)dot`

Explanation

Given points are A(1,-1,2),B(2,0,-1) and C(0,2,1)
`Rightarrow vec(AB)=veca=hati+hatj-3hatk,vec(BC)=vecb=-2hati+2hatj+2hatk`
`vecaxxvecb=|{:(hati,hatj,hatk),(1,1,-3),(-2,2,2):}|=8hati+4hatj+4hatk`
Hence, Unit vector `vecaxxvecb=|{:(hati,hatj,hatk),(1,1,-3),(-2,2,2):}|=8hati+4hatj+4hatk`