Here is the problem:
As you know, when a course ends, students start to forget the material they have learned. One model (called the Ebbinghaus model) assumes that the rate at which a student forgets material is proportional to the difference between the material currently remembered and some positive constant, . A. Let be the fraction of the original material remembered weeks after the course has ended. Set up a differential equation for , using as any constant of proportionality you may need (let ). Your equation will contain two constants; the constant (also positive) is less than for all .
I've found the equation is k(a-y)
but it also asks what the initial condition of the equation is?
and I cannot figure this part out.