Answer
$\lt 4,-10\gt$ and $2 \sqrt {29}$
Work Step by Step
Since, $-2v=-2\lt -2,5 \gt =\lt 4,-10\gt$
The magnitude of a vector is:$|n|=\sqrt{n_1^2+n_2^2}$
Now, $|\lt 4,-10\gt|=\sqrt{4^2+(-10)^2}=\sqrt {116}=2 \sqrt {29}$
Thus,answers are: $\lt 4,-10\gt$ and $2 \sqrt {29}$
