@Preben Alsholm Yes Z(r) is an arbitrary function.thankyou so much for the help.

@mehdi jafari i dont have to use boundary conditions.

Z(r) is function of integration

xi(r) is mass function

c is just a constant

@Preben Alsholm sorry, actually i was finding trouble to see my post.but i was about to delete it,because i got the old one.next time i will b careful

@Preben Alsholm Z(r) is function of integration .

@Preben Alsholm

agree & (d(C(t,r))/dt)^2  means 2nd derivative.

@mehdi jafari

equation is well typed ,but the is solution is very different from the expression which i want.