Chapter 12 - Vectors and the Geometry of Space - 12.4 The Cross Product - 12.4 Exercises - Page 861: 10

$k \times (i -2j)=2i+j$

Cross product of a vector with itself is zero. As we are given that $k \times (i -2j)$ $k \times (i -2j)=k \times i- 2k \times j$ $=k \times i+2j \times k$ $=j+2i$ Hence, $k \times (i -2j)=2i+j$