Question

Use the dot product to find v when v=(-2 -1)
a. -1 c. √5
b. -3 d. √3

Answer 1

Since you're only given the one vector, I assume you're supposed to find the magnitude of v, or ||v||, using the dot product.

We have

v • v = (-2, -1) • (-2, -1) = (-2)² + (-1)² = 5

so that

||v|| = √(v • v) = √(5)

and the answer is C.