The variational method is based on the theory of critical point,which could prove the existence,multiplicity,and approximate solution by transforming the differential equation boundary value problem into a variational problem.We study two different elliptic differential equations,namely the semilinear elliptical equation with critical exponent and the quasilinear elliptic equation with p-Laplacian operator by using the variational method in this paper.In the issue,we study the following semilinear elliptical equation with critical exponent where 2*=2N/N-4 is called critical Sobolev exponent.0 ?(?)RN(N ? 5)is a bounded smooth domain,1 ? ?<2,and0<?<?N,p=(N(N-4)/4)2.By using Ekeland's variational principle,we study the existence and multiplicity of nonzero non-negative solutions when ?take different values by establishing radial-off function.And we study the following quasilinear elliptic equation with p-Laplacian operator(?)where 0 ??(?)RN(N ? 5)is a bounded smooth domain,0<?<?N,p=((p-1)N(N-2p/p2)p and 0<q<1<?<p*-1,the p*=Np/N-2p is called critical Sobolev exponent.f(x)>0 and W(x)is a given function with the set {x??:W(x)>0} of positive measure.Using the concentration compactness principle and Nehari manifold,we obtain the existence and multiplicity of nonzero non-negative solutions and provide uniform estimates of extremal values by variational methods. |