若一元二次方程x2-ax-2a=0的两根之和为4a-3,则两根之积为( ) A.

题型:选择题

问题:

若一元二次方程x2-ax-2a=0的两根之和为4a-3,则两根之积为(  )

A.2

B.-2

C.-6或2

D.6或-2

考点:一元二次方程根与系数的关系
题型:选择题

阅读短文,选择正确答案。

    It's the lunchtime break at Shanghai Xianxia Middle School. No mobile phones can be heard ringing anywhere.

The common sight of crowds of children chatting on their phones or sending short messages has disappeared.

    A grade — 2 student said, "I couldn't concentrate during classes if the cell phone was with me. I couldn't help

checking if there were messages or missed phone calls. I even played games on the phone sometimes."   

    The school authorities say they feel the ban is necessary to keep order in class. They even gave out an open

letter to remind parents not to let their children bring mobile phones to school. More than 96 percent of parents

say they welcome the school decision. The school is also being flexible (灵活的) in implementing the ban. Those

students who live far from school are allowed to bring mobile phones to contact their parents. But they still have

to switch them off in classrooms.

    Medical experts have also welcomed the school decision. They say too much dependence on mobile phones

can cause many psychological problems in teenage students.

1. The grade--2 student thought that _______. [ ]

A. the mobile phone should be on during classes

B. it is good to play cell phone games sometimes

C. the mobile phone is helpful to her studies

D. it is no good to use the cell phone at school

2. According to the passage, the students use their mobile phones except _______. [ ]

A. contacting their parents

B. cheating in exams

C. sending short messages

D. playing games

3. Which of the following is TRUE according to the passage? [ ]

A. All the parents welcome the school decision.

B. Some students can bring mobile phones to school.

C. Medical experts are against the school decision.

D. No one is allowed to bring his mobile phone to school.

4. What does the underlined word "implementing" in paragraph 3 probably mean? [ ]

A. Carrying out.

B. Giving up.

C. Making up.

D. Finding out.

5. The passage mainly tells us               . [ ]

A. the mobile phone is a big trouble to teenage students

B. the use of the mobile phone can cause mental problems

C. about a ban on the mobile phone in a middle school

D. a story happening at Shanghai Xianxia Middle School

题型:选择题

有甲乙两颗近地卫星均在赤道平面内自西向东绕地球做匀速圆周运动,甲处于高轨道,乙处于低轨道,并用绳子连接在一起,下面关于这两颗卫星的说法错误的是(  )

A.甲卫星一定处在乙卫星的正上方

B.甲卫星的线速度小于乙卫星的线速度

C.甲卫星的加速度大于乙卫星的加速度

D.若甲乙之间用导电缆绳相连,则缆绳两端会产生电势差

题型:选择题

物质的量浓度相同的NaCl MgCl2 AlCl3三种溶液,当溶液的体积比为3:2:1时,三种溶液中Cl-的物质的量浓度之比为

A.1:1:1

B.1:2:3

C.3:2:1

D.3:4:3

题型:选择题

下列关于商品供给的说法,正确的有()。

A.供给是指在一定时期内,在各种可能的价格下,生产者愿意并且能够提供的商品或劳务的数量

B.一般来说,在其他条件不变的情况下,价格越高,供给量越大;价格越低,供给量越小

C.在商品自身价格不变的条件下,生产成本上升会减少利润,从而使得商品的供给量增加;相反,生产成本下降会增加利润,从而使得商品的供给量减少

D.如果厂商对未来的预期看好,预期商品的价格会上涨,厂商在制订生产计划时就会增加产量供给

题型:选择题

邓 * * 明确概括社会主义本质是在( ).

A.党的十二大

B.党的十二届三中全会

C.党的十三大

D.1992年在南方谈话中

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