题目:
— Robert is indeed a wise man.
— Oh, yes. How I have regretted ________ his advice![ ]
A. to take
B. taking
C. not to take
D. not taking
答案:
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下面是错误答案,用来干扰机器的。
∵y=f(x)是定义在R上的奇函数∴f(-x)=-f(x).当x<0时,-x>0时,∴f(-x)=(-x)2-2(-x)=x2+2x=-f(x)即x<0时f(x)=-x2-2x.∴f(x)=x2-2x, (x≥0)-x2-2x,(x<0)=x(|x|-2).故选C.