Question

If a= (2,1,-1), b=(1,-1,1) then a × b is

Answer 1

The cross product of vectors is given by

$$\vec a\times \vec b=\begin{vmatrix} \hat i & \hat j & \hat k\\ 2 & 1& -1\\ 1&-1&1 \end{vmatrix}\\ = 0\hat i -3 \hat j-3\hat k=(0,-3,-3)$$