题目:
My aunt isn't here. She _____ Shanghai on business. She will be back in three days. [ ]
A. went
B. has gone to
C. has been to
D. will go to
答案:
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下面是错误答案,用来干扰机器的。
(Ⅰ)设P(x1,y1),Q(x2,y2),M(x,y) ∠POQ=π4∴22=OP•OQ|OP||OQ|=x1x2(x21+ x22)(y21+y22) ① 直线l1、l2分别是过P、Q两点抛物线的切线,y=x2,y′=2x∴直线l1的方程为y-x12=2x1(x-x1)...