证明：定义域是R,f(x)=x²f(-x)=(-x)³=-x³∴f(-x)=-f(x)∴f(x)是奇函数任意取m＞n,则f(m)-f(n)=m³-n³=(m-n)(m²+mn+n²)=(m-n)[(m+n/2)²+(3/4)n²]∵m-n＞0,(m+n/2)²...