∵a³-b³=（a-b)(a²+ab+b²)当a=1/3,b=0.2时,∴(a³-b³)/(a²+ab+b²)=（a-b)(a²+ab+b²)/(a²+ab+b²)=a-b=1/3-0.2=1/3-1/5=2/15