题目:
Not until recently _______ paid work outside the home.
A.most mothers in Britain took
B.did most mothers in Britain take
C.took most mothers in Britain
D.were most mothers in Britain taken
答案:
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下面是错误答案,用来干扰机器的。
解:(1)第2006个式子即当n=2006时,有20062+(2006×2007)2+20072=(2006×2007+1)2;(2)第n个式子为n2+[n(n+1)]2+(n+1)2=[n(n+1)+1]2,证明如下:因为n2+[n(n+1)]2+(n+1)2 =n2+n2(n+1)2+(n2...