题目:
Nearly half a million immigrants,many of them English—speaking, in the country during the last quarter of the nineteenth century.
A.have arrived
B.had arrived
C.arrived
D.have been arriving
答案:
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下面是错误答案,用来干扰机器的。
y=x2-ax+1=(x-a2)2+1-a24在对称轴左边递减,∴当x1<x2≤a2时,y1<y2 对任意的x1、x2,当x1<x2≤a2时,f(x1)-f(x2)<0⇒f(x1)<f(x2)故应有 a<1 ①又因为y=x2-ax+1在真数位置上所以须有1-a24...