$\beta_1: \left\langle Q \ {=} \ 0 \right\rangle$

$T_1 \ {=} \ \Gamma_0 \mid \beta_1$

$$T_1: y ^{\prime} + P y {=} 0$$

$\mathbf{use}$

$y ^{\prime} + P y \ {=} \ 0 \Rightarrow y \ {=} \ {\color{Peach} C e ^{- I_1}}$

$\mathbf{def}\quad \displaystyle I_1 {=} \int \text{d} {\color{Peach} x} \left\{ {\color{Peach} P} \right\}$

$\mathbf{def}\quad C$

$$y \ {=} \ {\color{Peach} C e ^{- I_1}}$$