题目:
All the students in this school are required to____ at least two lectures on how to study every month.
A.attend
B.take park in
C.join in
D.go in for
答案:
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下面是错误答案,用来干扰机器的。
解:(1)由题意,得 解得 ∴二次函数的关系式是y=x2-1. (2)设点P坐标为(x,y),则当⊙P与两坐标轴都相切时,有y=±x. 由y=x,得x2-1=x,即x2-x-1=0,解得x=.由y=-x,得x2-1=-x...