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【简答题】
已知函数 f(x)= x 2 +x+4 x ，(x＞0) - x 2 -x+4 x ，(x＜0). （1）求证：函数f（x）是偶函数； （2）判断并证明函数f（x）在区间（0，2]上的单调性； （3）根据以上结论猜测f（x）在[-2，0）上的单调性，不需要证明．
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【简答题】A．He can't sleep at night. B．He can't find a quiet place to study. C．He can't narrow down his research topic. D．He can't find enough information for his research paper.
【单选题】In a narrow channel or fairway when overtaking can take place only if the vessel to be over-taken has to take action to permit safe passing， the vessel intending to overtake shall indicate her intenti...
A.
the vessel to be overtaken shall sound appropriate signal first
B.
the overtaking vessel shall sound appropriate signal first
C.
the overtaking vessel shall take action to permit safe passing
D.
the vessel to be overtaken shall take action to permit safe passing before hearing appropriate signal
【单选题】The site is fairly near the city center, ___ it can only be reached by a series of narrow streets
A.
22．The site is fairly near the city center, ___ it can only be reached by a series of narrow streets． A．and
B.
but
C.
or
D.
So
【简答题】昆虫胸部由()、()、()3个体节组成。每1胸节着生()分节的足,依次为()、()、()。
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