x=0
f(-0)=f(0)=-f(0)=0
f(0)=0
当x＞0时f(x)=x3+2x2-1
当x0
f(-x)=-x^3+2x^2-1=-f(x)
f(x)=x^3-2x^2+1
分段函数
f(x)={
f1=x3+2x2-1(x>0)
f2=0(x=0)
f3=x^3-2x^2+1(x