<p>I think there may be some doubts about the question's suitability for CV insofar as it asks for something different from the suggested duplicate. In no particular order:</p>

<ol>
<li><p>Deriving a solution for the equations in non-matrix form is more
Maths than Statistics.</p></li>
<li><p>The desired form for the answer can be got by Googling or
with a computer algebra system. (Lack of research effort.)</p></li>
<li><p>No-one needs to be able to calculate coefficient
estimates by hand nowadays&mdash;&amp; the numerical accuracy of results arrived at this way might well be an issue.</p></li>
<li><p>There doesn't seem much point in making of CV a compendium of results
for particular cases.</p></li>
<li><p>Working out the answer would aid understanding more than looking
at it. (Is it a homework question?)</p></li>
</ol>

<p>Nonetheless, these considerations don't seem overwhelming, &amp; I couldn't see any harm in re-opening it (when I did it already had two re-open votes).</p>
