Solution (source code)

= Solution

Subtract the two position <vectors> to obtain the direction $\mathbf b-\mathbf a=(-3,-1,3)$. The <affine line in a vector space> through the points is therefore
$$
\boxed{\mathbf r=(2,-1,-2)+t(-3,-1,3),\qquad t\in\mathbb R.}
$$
The values $t=0,1$ recover the two specified points.