因为根号下一定大于等于0
所以4-(x²-5x+2)²>=0
所以(x²-5x+2)²=<4
所以-2<=x²-5x+2=<2
分解为不等式x²-5x+2<=2和-2<=x²-5x+2
分别解之,得：
0<=x<=5且 x<=1或x>=4
所以0<=x<=1或4<=x<=5