PURSUIT CURVE (differential geom)

I have here a problem in my Diff. Geom class.

----> Suppose an enemy plane begins at (0,0) and travels up the y-axis at constant speed A missile is fired at (a,0) with speed and the missile has a heat sensor which always directs it toward the plane.

1.] Show that the pusuit curve which the missile follows is given implicitly by the differential-integral equation

2.] Differentiate this expression to get a separable diff. eq. Integate to get the closed form expression fo the pusuit cuve

I already finished no.1. I did no.2 but I got a slightly different answer from the right hand side of the eq. there. Can someone help me out?