无编号
\begin{align*} p(f_1=0) &= 0.8/0.9*p(s_1=0)+0.1/0.9*p(s_2=0) \\ &= 0.8/0.9*0.4+0.1/0.9*0.6 \\ &= 0.4222 \end{align*}
有编号
\begin{align} & &-e^{-\Phi} \Phi'(a^3 \Phi v) + e^{-\Phi} \Phi_z(a^3 \Phi v) &= a^5 e^{-\Phi}m_X^2 v + a^5 e^{-\Phi} \frac{\lambda}{2}v^3 \nonumber \\ \Longrightarrow & &- \Phi'(a^3 \Phi v) + \Phi_z(a^3 \Phi v) &= a^5 m_X^2 v + a^5 \frac{\lambda}{2}v^3 \nonumber \\ \Longrightarrow & &a^3 v'(- \Phi') + (a^3 v')' &= a^5 (m_X^2 v + \frac{\lambda}{2}v^3) \\ \label{phi'1} \Longrightarrow & &a^3 v' - a^5 ( m_X^2 v + \frac{\lambda}{2} v^3 ) &= a^3 v' \Phi'\nonumber \end{align}