（1-x+2分之3）÷(x+2)分之(x平方-2x+1) 化简后 x=1+根号2
=(x+2-3)/(x+2)÷(x-1)²/(x+2)
=(x-1)/(x-1)²
=1/(x-1)
=1/(1+√2-1)
=1/(√2)
=(√2)/2