Let $u=($:$1,-4$:$)$ and $v=($:$-4,2$:$).$ Find the component form and magnitude $($length$)$ of the vector $2u-4v.$

The component form is $2u-4v=$

$($Simplify your answers.$)$

The magnitude is $|2u-4v|=$

$($Type an exact answer, using radicals as needed.$)$