\newsectionNoPB
\subsection{Linear differential equations of first order}
\shade{gray}{Homogeneous equation} Move all $y$ to one side and all other vars to other. Integrate both

\shortproposition Solution of $y' + ay = 0$ is of form $f(x) = z e^{-A(x)}$ with $A$ anti-derivative of $a$

\TODO Improve procedure with notes from session \& SPAM