1. The problem statement, all variables and given/known data Discuss the motion of a particle in a central inverse-square-law force field for a superimposed force whose magnitude is inversely proportional to the cube of the distance from the particle to the force center, that is: F(r) = -k/r2 - λ/r3 and k,λ>0Show that the motion is described by a precessing ellipse. 2. Relevant equations The one given in the question 3. The attempt at a solution I honestly don't know where to begin, we derived an equation in class that we could find the force law if a particular known orbit r=r(θ), and I was thinking of using it: (d2/dθ2)(1/r) + (1/r) = -μr2F(r)/l2but I don't know what to do with the left hand side, but again it's just a guess as to what to start with. Sorry for not using the math commands, they didn't want to work for some reason.