  We will investigate the asymptotic behavior of positive solutions of the
elliptic equation \Delta u+|x|^{l_{1}}u^{p}+|x|^{l_{2}}u^{q}=0 {in} R^{n}. We
establish that for $n\geq 3$ and $q>p>1$, any positive radial solution of (0.1)
has the following property: $\lim_{r\to\infty}r^{\frac{2+l_{1}}{p-1}}u$ and
$\lim_{r\to0}r^{\frac{2+l_{2}}{q-1}}u$ always exist if
$\frac{n+l_{1}}{n-2}<p<q, p\neq\frac{n+2+2l_{1}}{n-2}, q
\neq\frac{n+2+2l_{2}}{n-2}.$ In addition, we prove that the singular solution
of (0.1) is unique under a certain condition
