Uniqueness of Positive Solutions for Some Nonlinear Fourth-Order Equations

In this paper we study the uniqueness question of positive solutions of the two point boundary value problem:u 4. t.sf u t..,yR-t-R, u "R.suX "R.s 0, where R)0 is fixed and f :w0,`.ªw0, `. is in C1. A uniqueness result is proved when f satisfies 0-f u.-ufX u. for u)0. Some examples are also given.