# Solution to #4-1

Paper 1 Difficulty:Medium

Let $\vec{v}=\begin{pmatrix} 1\\ 2\\ 3 \end{pmatrix}$, and $\vec{w}=\begin{pmatrix} -3\\ 1\\ 2 \end{pmatrix}$.

If $\vec{u}=\vec{v}-2\vec{w}$, find the magnitude of vector $\vec{u}$.

[Maximum mark:5]