求二元函数f(x,y)=x3+8y3-xy的极值。
SinceWilliamhadbeenseriouslyillforseveralmonths,hisparentswereworriedabout________toreturntoschoolfull-time.
A、hewanted
B、hewanting
C、himtowant
D、hiswanting
Themorewelookedatthepicture,________.
A、thelesswelikedit
B、welikeitless
C、betterwelikedit
D、itlookedbetter
A、合同且相似
B、合同但不相似
C、不合同但相似
D、不合同且不相似
Theproblem________whenthestudentsrefusedtodotheirhomework.
A、arose
B、aroused
C、rose
D、raised