解：?$(2)$?把?$x=k$?代入?$y=-x-1，$?得?$y=-k-1，$?
則?$A_1$?的坐標(biāo)是?$(k，$??$-k-1)；$?
把?$x=k$?代入?$y=\frac {1}{x}$?得：?$y=\frac {1}{k}，$?
則?$B_1$?的坐標(biāo)是?$(k，$??$\frac {1}{k})；$?
把?$y=\frac {1}{k}$?代入?$y=-x-1$?得：?$\frac {1}{k}=-x-1$?
解得：?$x=-\frac {k+1}{k}，$?即?$A_2$?的坐標(biāo)是?$(-\frac {k+1}{k}，$??$\frac {1}{k})；$?
把?$x=-\frac {k+1}{k}$?代入?$y=\frac {1}{x}$?得：?$y=-\frac {k}{k+1}$?
則?$B_2$?的坐標(biāo)是?$(-\frac {k+1}{k}，$??$-\frac {k}{k+1})$?
把?$y=-\frac {k}{k+1}$?代入?$y=-x-1，$?得：?$x=-\frac {1}{k+1}$?
即?$A_3$?的坐標(biāo)是?$(-\frac {1}{k+1}，$??$-\frac {k}{k+1})；$?
把?$x=-\frac {1}{k+1}$?代入?$y=\frac {1}{x}$?得：?$y=-k-1$?
則?$B_3$?的坐標(biāo)是?$(-\frac {1}{k+1}，$??$-k-1)$?
把?$y=k+1$?代入?$y=-x-1$?得?$x=k，$?則?$A_4$?的坐標(biāo)是?$(k，$??$-k-1)，$?即?$A_1$?
則點?$A_{n}$?的橫坐標(biāo)分別是：?$k，$??$-\frac {k+1}{k}，$??$-\frac {1}{k+1}，$?···三個循環(huán)一次
