The present paper is concerned with the problem of approximating a given element of a linear space by a family of elements, depending on a parameter, as well as possible. Normlike convex functionals are used as measures for the quality of approximation. By means of quasilinearization of the convex approximation measure the approximation problem is transformed into a maximin. or programming problem, which is sometimes dealt with much easier. From the maximim-formulation a dual problem, replacing the primal approximation problems, is derived with the aid of a maximin-theorem of Ky Fan. New resultats on linear Chebyshev approximation with restricted parameters are obtained in this manner.