1、当x≤0时，f(x)≥x²，(x+2)^2>=x^2，4x+4>=0,x>=-1此时，-1<=x<=02、当x>0时，f(x)≥x²，(-x+2)^2>=x^2,4x<=4,x<=1此时，0综上，-1<=x<=1
