阅读下面这首诗。
                                                                                                                                       秋夜山居
                                                                                                                                       唐•施肩吾
                                                                                                                去雁声遥人语绝，谁家素机①织新雪。
                                                                                                                 秋山野客②醉醒时，百尺老松衔半月。
       【注释】①素机：织布机。②野客：离乡在外的游客。

函数f（x）=（$\frac{1}{2}$）^{$\sqrt{x^2-x-2}$}的单调递增区间为（　　）