Some embedding inequalities in Hardy-Sobolev space are proved. Furthermore, by the improved inequalities and the linking theorem, in a new k-order Sobolev-Hardy space, we obtain the existence of sign-changing solutions for the nonlinear elliptic equation
\left\{\disp−Δ(k)u:=−Δu−(N−2)24u|x|2−14k−1∑i=1u|x|2(ln(i)R/|x|)2=f(x,u),x∈Ω,u=0,x∈∂Ω,
\right.
where 0\in \Omega \subset B_a(0)\subset {\Bbb R}^N, N\geq 3, \ln_{(i)}=\prod\limits_{j=1}^i\ln^{(j)}, and R=ae^{(k-1)}, where e^{(0)}=1, e^{(j)}=e^{e^{(j-1)}} for j\geq 1, \ln^{(1)}=\ln, \ln^{(j)}=\ln\ln^{(j-1)} for j\geq 2. Besides, positive and negative solutions are obtained by a variant mountain pass theorem.
