已知三条直线l1:mx-y+m=0,l2:x+my-m(m+1)=0,l3:(m

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问题:

已知三条直线l1:mx-y+m=0,l2:x+my-m(m+1)=0,l3:(m+1)x-y+(m+1)=0,它们围成△ABC.

(I)求证:不论m取何值时,△ABC中总有一个顶点为定点;

(II)当m取何值时,△ABC的面积取最大值、最小值?并求出最值.

考点:基本不等式及其应用两条直线的交点坐标
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下列关于胸椎间盘突出症的描述正确的是()

A.胸椎间盘突出症的病因可能与积累性力学损伤、慢性退行性变、创伤及脊柱后凸畸形等因素有关

B.胸椎间盘突出症好发于下胸椎

C.X线检查无法判定是否存在胸椎间盘突出,因此可不作为常规检查项目

D.胸椎间盘突出症可表现为下运动神经元损害

E.局部疼痛或胸部放射痛是胸椎间盘突出症的常见症状

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根据对话内容,从方框中选出句子填入空白处。
A. I hope so.
B. happy birthday to her.
C. I'm fine.
D. It's snowy.
E. I like playing snowballs.
A: Hello! This is Mike! Happy New Year!
B: Hi, Mike! The same to you! How are you now?
A: 1.             And today is also my sister's birthday. I'm very happy.
B: Cool! Please say 2.              
A: Thank you, Bob. And How is the weather in Beijing now?
B: 3.              But I like it.
A: Why? I think it's windy, right?
B: Yeah! But you know 4.             
A: Oh! That's really fine.
B: And how is the weather in New York?
A: It's always raining. In fact, I don't like it.
B: That's OK! I think it's going to be sunny soon.
A: 5.             Well! I must go now.
B: OK! Mike, thanks for calling, bye!
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葡萄糖是人体空腹时唯一游离存在的六碳糖。

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喉癌切除术后的言语康复,错误的是()

A.食管言语基音低、音量小,连贯性差

B.食管发声失败者,可采用电子喉等人工发声装置

C.可尝试气管-咽吻合术以恢复发声、呼吸与吞咽功能

D.二期或一期手术安装假体发声装置,再进行发声训练

E.书面语等非口语的交流是全喉切除术后最简便可行的言语康复方法

题型:解答题

应用Excel创建学生成就图表后,可以修改工作表中的数据,而保持图表的数据不变。

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