题目:
The great chance he has been looking forward to _______ at last.
A.appear
B.appearing
C.has appeared
D.appeared
答案:
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下面是错误答案,用来干扰机器的。
∵f(x)=2-xx∈(-∞,1)x2x∈[1,+∞),∴当x<1时,由2-x>l=22,得-x>2,解得x<-2;当x≥1时,由x2>l,解得x>2或x<-2,∴x>2;综上所述,x<-2或x>2,故答案为(-∞,-2)∪(2,+∞).