Chapter 9 - Polar Coordinates; Vectors - 9.6 Vectors in Space - 9.6 Assess Your Understanding - Page 625: 27

$3i+4j-k$

If a vector $v$ initiates at point $P_1(x_1,y_1,z_1)$ and terminates at $P_2(x_2,y_2,z_2)$ then $v$ is equal to the position vector $v=(x_2-x_1)i+(y_2-y_1)j+(z_2-z_1)k.$ Hence, here $v=(3-0)i+(4-0)j+(-1-0)k\\ v=3i+4j-k$