Answer
$v=2i-4j$
$||v||=2\sqrt5$
Work Step by Step
If a vector $v$ initiates at point $P(x_1,y_1)$ and terminates at $Q(x_2,y_2)$ then $v==(x_2-x_1)i+(y_2-y_1)j.$
Hence, here
$v=(3-1)i+[-6-(-2)]j\\
v=2i-4j$
The magnitude of a vector $v=ai+bj$ is:
$||v||=\sqrt{a^2+b^2}$.
Thus,
$||v||=\sqrt{2^2+(-4)^2}=\sqrt{4+16}=\sqrt{20}=2\sqrt5$