1e4765…: “Onto a funny line”

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Find a unit vector $\vec {u}$ in the direction of $\begin{bmatrix}7\\-1\\5\end{bmatrix}$

\[\vec {u}=\answer {\frac {1}{\sqrt {75}}}\begin{bmatrix}7\\-1\\5\end{bmatrix}\]

Enter the exact answer. No decimal approximations.

Source

[Nicholson] W. Keith Nicholson, Linear Algebra with Applications, Lyryx 2021, Open Edition, Problem 4.1.2(a).