Solution
= Solution
The <orthogonal projection> of the origin onto the <line> occurs at $t_*=-p\cdot u/|u|^2=-1/5$, giving closest point $(2,4/5,-2/5)$. Hence the <distance from a point to a line in three dimensions> is
$$
\boxed{d=\sqrt{4+\frac{16+4}{25}}=\sqrt{\frac{24}{5}}=\frac{2\sqrt{30}}5.}
$$