ON THE EXISTENCE OF THE THIRD SOLUTION OF THE NONLINEAR BIHARMONIC EQUATION WITH DIRICHLET BOUNDARY CONDITION

We are concerned with the multiplicity of solutions of the nonlinear biharmonic equation with Dirichlet boundary condition, ${\Delta}^2u+c{\Delta}u=g(u)$, in ${\Omega}$, where $c{\in}R$ and ${\Delta}^2$ denotes the biharmonic operator. We show that there exists at least three solutions of the above problem under the suitable condition of g(u).