题目

With all the responsibilities（责任） we face in our daily lives, it’s often hard to get a good night’s rest. The problem really lies in the stress that many of us experience. Stress robs you of the rest that you need by putting you in a state of pressure and worry. There are, of course, some methods that can help you relax, but only a few of them give you a good night’s sleep. One of them is soothing (舒缓的)music for sleep. Sleep music is not just for encouraging relaxation, it also can be used for various situations. Want to have a relaxing evening by yourself? Practice 设实数x，y满足不等式组2x-y-1≥04x-y-6≤02x+y-k-2≥0，且4x2+y2的最小值为m，当9≤m≤25时，实数k的取值范围是 ．