Optimizing xlog(1+y/x)

[Mark_L_Stone]

-rel_entr(x,x+y)

Problem to express x*log(1+c/x)

Hello guys, I met a problem while using cvx. My objective function is f(x) = x*log(1+c/x),x>0, where c is a constant. The function is convex, but I don’t know how to express which in cvx. Can you help me? Thanks!