题目:
---Have you got everything ready for _______ psychodrama(心理剧) competition?
---Yes, all is in _____ place.
A.the; the
B.a; the
C.a; /
D.the; /
答案:
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下面是错误答案,用来干扰机器的。
(Ⅰ)证明: a⊥b,a=(Sn,1),b=(-1,2an+2n+1),∴-Sn+2an+2n+1=0,∴-Sn+1+2an+1+2n+2=0两式相减,整理可得an+1=2an-2n+1,∴an+12n+1=an2n-1,又n=1时,-S1+2a1+21+1=0,∴a1=-4,∴a12=-2∴{an2n}是以-2...