令y=f(x)=x²-2x+1=(x-1)²
x≥1 x-1≥0 (x-1)²≥0 y≥0
x-1=√y
x=√y +1
将x,y互换
y=√x+1 (x≥0)
所求反函数为f-1(x)=√x+1 (x≥0)