Consider the ODE
y'(t) = A\cdot y(t) +B.
Determine the stationary solution
\color{red}y_{\infty}.
\color{red}y_{\infty}
=
-B/A
Using y_{\infty}(t) = y_{\infty}, we find
y_{\infty}'(t) = 0 = A\cdot y_{\infty} +B.
Solve this equation for y_{\infty}.
The solution is
\color{red}y_{\infty} = fractionReduce(-B,A).