解答如下图片：
根号x^2-2x+1+根号x^2-6x+9括号1<=x<=3=√x²-2x+1+√x²-6x+9=|x|-2x+1+|x|-6x+9=2|x|-8x+10因为1<=x<=3所以=2x-8x+10=10-6x-8≤10-6x<4
