`u = ` Use the dot product to find the magnitude of u.

The magnitude of a vector `u` is the square root of its product by itself, because

`u*u=||u||*||u||*cos(theta),`

and `theta=0,` `cos(theta)=1.` So

`||u||=sqrt(u*u)=sqrt(lt-8,15gt*lt-8,15gt)=` `=sqrt((-8)*(-8)+15*15)=sqrt(64+225)=sqrt(289)=17.`

This is the answer.

The magnitude of a vector `u` is the square root of its product by itself, because

`u*u=||u||*||u||*cos(theta),`

and `theta=0,` `cos(theta)=1.` So

`||u||=sqrt(u*u)=sqrt(lt-8,15gt*lt-8,15gt)=`
`=sqrt((-8)*(-8)+15*15)=sqrt(64+225)=sqrt(289)=17.`

This is the answer.