At x = y = 1, one of the eigenvalues of the Hessian of log(1+(x/(1+y)) is negative, and the other is positive. Therefore, the function is neither convex nor concave, and can’t be used in CVX.
At x = y = 1, one of the eigenvalues of the Hessian of log(1+(x/(1+y)) is negative, and the other is positive. Therefore, the function is neither convex nor concave, and can’t be used in CVX.