已知x、y满足|x-2y+a|+(x-y-2a+1)2=0且x-3y<-1,求a

题型:解答题

问题:

已知x、y满足|x-2y+a|+(x-y-2a+1)2=0且x-3y<-1,求a的取值范围.

考点:有理数的乘方二元一次方程组的解法
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分析下表中某大肠杆菌细胞的分子组成,能够得到的推论是

[ ]

A.一个DNA分子只控制一种蛋白质的合成

B.DNA是主要的遗传物质

C.蛋白质是细胞中含量最多的有机化合物

D.一个DNA转录出6种RNA

题型:解答题

阅读下面短文,从短文后各题所给的四个选项(A、B、C和D)中,选出可以填入空白处的最佳选项,并在答题卡上将该项涂黑。学科&网

Hundreds of people have formed impressions of you through that little device(装置) on your desk. And they’ve never actually   41   you. Everything they know about you   42   through this device, sometimes from hundreds of miles away.   43   they feel they can know you   44   from the sound of your voice. That’s how powerful the   45   is.

Powerful, yes, but not always   46  . For years I dealt with my travel agent only by phone. Rani, my faceless agent whom I’d never met   47  , got me rock-bottom prices on airfares, cars, and hotels. But her cold voice really   48   me. I sometimes wished to   49   another agent.

One morning, I had to   50   an immediate flight home for a family emergency. I ran into Rani’s office   51  . The woman sitting at the desk,   52   my madness, sympathetically jumped up. She gave me a   53   smile, nodded while listening patiently, and then printed out the   54   immediately. “What a wonderful lady!” I thought.

Rushing out   55   I called out over my shoulder, “By the way, what’s your name?” “I’m Rani,” she said. I turned around and saw a   56   woman with a big smile on her face waving to wish me a safe trip. I was   57  ! Why had I thought she was cold? Rani was, well, so   58  .

Sitting back in the car on the way to the airport, I figured it all out. Rani’s   59  ---her warm smile, her nods, her ‘I’m here for you’   60  ---were all silent signals that didn’t travel through wires.

49()

A. promote

B. train

C. find

D. know

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青春期对营养的要求是[ ]

A.多吃肉,不吃蔬菜

B.多吃蔬菜,少吃肉

C.随便吃一点,有什么吃什么

D.全面合理的膳食

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PEG-20M气相色谱固定液的极性属于是()。

A.非极性

B.中等极性

C.极性

题型:解答题

下列关于血栓闭塞性静脉炎的特征描述正确的是()

A.没有间歇性跛行

B.游走性血栓性浅静脉炎

C.累及内脏

D.肢体皮肤正常

E.与酒精中毒有关

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