（-1，0）
Thedirectorrecommendedthatshe________(study)moreEnglishbeforegoingabroad.
求二元函数f(x,y)=x3+8y3-xy的极值。
I'msorryIforgottowrite;Ihadsomuchelse________mymind.
设函数y=sinx^2+2x，求dy.
WeweretoldthatSuewouldbeidealforthejob,butshe________badlywhenwetalkedtoher.
