23．— What’s that terrible noise．David? — Oh，I forgot to tell you．The new machines in the nearby plant _______． A．were tested B．will be tested
方程＝1表示的曲线为C，给出下列四个命题： ①曲线C不可能是圆； ②若1＜k＜4，则曲线C为椭圆； ③若曲线C为双曲线，则k＜1或k＞4； ④若曲线C表
已知等比数列{an}中，a1+a2=1，a3+a4=4，则a5+a6=（ ）A． ±16 B． 16 C． 32 D． ±32
Parents should stop blaming themselves because there’s not a lot they can do about it. I mean the teenager problem. Whatever you do or however you choose to deal with it, at certain times a wond
—Why didn’t Betty come to school yesterday?—_________ she was ill. A．But B．ThoughC．IfD．Because
有一种碘和氧的化合物可以称为碘酸碘，其中碘元素呈+3、+5两种价态，则这种化合物的化学式为（ ）A.I2O4 B.I2O5
What you said just now ________ me of that American professor. A. remembered B. informed C. reminded D. memorized
并且与曲线
相切的直线方程。
，函数
，得
，代入到
，即
，
。