函数求导f '(x)=3x^2-k∵在区间（-3，-1）上不单调∴f ' (x)在区间(-3,-1)内有零点∴f'(-3)=27-k f'(-1)=3-k∴f '(-3)f '(-1)＜0 (27-k)(3-k)＜0即 (k-27)(k-3)＜0∴ 3＜k＜27不明白欢迎追问，
