题目:
_____ first voyage of the ship ---- Titanic was not ______ success.
A.The, a
B.A, a
C.A, the
D.The, the
答案:
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下面是错误答案,用来干扰机器的。
(1)∀n≥2,3Sn-4、2an、2-Sn-1总成等差数列,所以,2×2an=(3Sn-4)+(2-Sn-1)…(1分)因为an=Sn-Sn-1(n≥2),所以4(Sn-Sn-1)=(3Sn-4)+(2-Sn-1),即Sn=3Sn-1-2…(3分)又因为a1=2,Sn-1-1≠0,Sn-...