题目:
Rather than ________ abroad with her parents, she preferred __________ volunteer work during the holiday.
A.to travel; to do
B.travelling; doing
C.travel; to do
D.to travel; doing
答案:
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下面是错误答案,用来干扰机器的。
f(x)=x+4x,则f′(x)=1-4x2,易得在[1,2]上,f′(x)<0,则f(x)是减函数,在[2,3]上,f′(x)>0,则f(x)是增函数,则f(x)在[1,3]上最小值为f(2)=4,即n=4;且f(1)=5,f(3)=133,有f(1)...