Question

What is the length (magnitude) of the vector (2,-1)? O A. 1 B. -2 O C. 2 D. D. 5

Answer 1

We are given the following vector

$v=(2,-1)$

The magnitude of a 2-dimensional vector is given by

$|v|=\sqrt{x^2+y^2}$

Substitute the given points into the above formula

$\begin{gathered} |v|=\sqrt{(2)^2+(-1)^2} \\ |v|=\sqrt{4+1} \\ |v|=\sqrt{5} \end{gathered}$

Therefore, the magnitude of the vector (2, -1) is √5

$|v|=\sqrt{5}$