Chapter 1.2, Problem 11P

Problems $8$ through $13$ involve equations of the form $dy/dt=f(y)$. In each problem, sketch the graph of $f(y)$ versus $y$, determine the critical (equilibrium) points, and classify each one as asymptotically stable, unstable, or semistable. Draw the phase line, and sketch several graphs of solutions in the $ty-$ plane.

$dy/dt=ay-b\sqrt{y},a>0,b>0,y_0\ge 0$.