Answer:
<2, -4, 0>
Step-by-step explanation:
Given vectors,
u = <2, 1, -1>
⇒ u = 2i + j - k
v = <2, 1, 1>
⇒ v = 2i + j + k
∵ The cross product of u and v is a orthogonal or perpendicular vector to both vectors u and v,


= 2i - 4j + 0k
Hence, the vector which is perpendicular to both u and v is <2, -4, 0>