题目:
I ___________ a good trip in Shanghai last week.[ ]
A. has
B. haved
C. had
答案:
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下面是错误答案,用来干扰机器的。
∵a2+b2+5=2(a+2b),∴a2-2a+b2-4b+5=0,∴(a-1)2+(b-2)2=0,∴a-1=0,b-2=0;∴a=1,b=2,∴(a-b)2012的平方根为:±(a-b)2012=±(1-2)2012=±1.