| In this paper,we investigate the existence and multiplicity of positive solutions for some quasilinear elliptic problems.In chapter1, using variational methods, we establish the existence of positive solutions for a class of quasilinear elliptic problem where△pu=div(|(?)u|p-2(?)u) with1<p<N,f:R→R is continuous having a subcritical growth and V is a nonnegative potential, which satisfies lim|x|→+∞V(x)=0.In chapter2, we investigate how the coefficient f(x) affects the number of posi-tive solutions of the following quasilinear elliptic systems where O∈Ω(?) RN is a bounded domain, a>1,β>1and1<p<q<a+β=p*=Np/N-p for N>2p. |