I have this exercise and I do not know how to solve it.
By using the method of isoclines represent the integrals of equation corbes nonautonomous $x'=x^2-t$.
There are some indications: Let $P = I_0$, the parabola $x^2 = t$. Show that $P^-$ is a trapping region ($P = P^+\cup P^-$).
How can we prove it?