Answer
$\vec{u}=\begin{bmatrix}
7/\sqrt{69}\\
2/\sqrt{69}\\
4/\sqrt{69}
\end{bmatrix}$
Work Step by Step
$\vec{v}=\begin{bmatrix}
7\\
2\\
4
\end{bmatrix}$
$||\vec{v}||=\sqrt{\vec{v}\cdot\vec{v}}=\sqrt{7^2+2^2+4^2}=\sqrt{69}$
$\vec{u}=\frac{\vec{v}}{||\vec{v}||}=\begin{bmatrix}
7/\sqrt{69}\\
2/\sqrt{69}\\
4/\sqrt{69}
\end{bmatrix}$
