f（x）=x^2 x＜=0 1+2x x＞0∫0--＞2[f（x-1）]dx令x-1=tx=0,t=-1;x=2,t=1原式=∫(-1,1)f(t)dt=∫(-1,0)t²dt+∫(0,1)(1+2t)dt=t³/3|(-1,0)+(t+t²)|(0,1)=0-(-1/3)+1+1-0=1/3+2=7/3