题干

如果 (3x2m1y2n1)(
1
3
xnym1
)
=x7y5
,m,n均为正整数,求m,n的值.
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答案(点此获取答案解析)

解: (3x2m1y2n1

同类题1

阅读课文《神奇的克隆》,回答问题。

    《西游记》里的孙大圣,紧急关头常常把下一把毫毛,再吹一口气,毫毛立刻变成了一群和自己一模一样的孙悟空。这当然是神话, 不过用今天的科学名词来讲,那就是孙悟空能够快速地克隆自己。  

     我们知道,高等动物一般要通过雄性和雌性生殖细胞的结合,才能繁衍后代,人们把这种繁殖叫做有性繁殖。换句话说,每只动物都有自 己的爸爸妈妈。如果不经过两性细胞结合而直接繁衍后代,就叫无性繁殖,也称克隆。  

     许多植物都有先天克隆的本领。例如,从一棵大树上剪下几根枝条插进土里,枝条就会长成一株株活泼可爱的小柳树;把马铃薯切成许 多小块种进地里,就能收获许多新鲜的马铃薯;把仙人掌切成几块,每块落地不久就会生根,长成新的仙人掌,此外,一些植物还可以通过压 ​条或嫁接培育后代。凡此种种,都是植物的克隆。  

      一些单细胞微生物,如细菌,经过20分钟左右的时间,就可以一分为二,再分为四个、八个,这就是低等生物的克隆。  

      那么,高等生物可不可以克隆呢?从20世纪开始,科学家在这方面进行了卓有成效的研究。1996年,英国科学家成功地克隆出了世界上的 一只克隆羊。这是一项了不起的成就,轰动了当时的科学界。科学家借用一名乡村歌手的名字,给这只克隆羊起名为“多利”。  

      克隆技术是一项可以造福于人类的科技成果。  

      人们将克隆技术与其他科技成果结合,可以根据需要培育出优质、高产的粮食、蔬菜新品种;也可以培育大量品质优良的家畜,大大提高 了饲养效率。  

      克隆技术还可以挽救一些濒危物种,让一些濒临灭绝的动物免遭厄运,从而调节大自然的生态平衡。人们利用克隆技术能够培植人体的皮 ​肤进行植皮手术;能够“制造”出人的耳朵、软骨、肝脏和心脏等人体“配件”,一旦病人需要,就能重新“装配”。  

     神奇的克隆技术正向人类展示它诱人的前景。



“克隆羊”的诞生,为什么在全世界引起“轰动”?

同类题5

任务型阅读

The Farmers' Fresh Market

    This morning,I went to the Farmers Market in Burlington ,Vermont. I didn't know what the Farmers Market is or how to get there.____

    First ,I had to decide how to go there,and I chose both to walk and to take a bus. When I went,I would walk and when I came back,I would take a bus.____

Walking to the market in this city,I was surprised because every house was beautiful,and they were all arranged in good order. In Korea's cities,most houses are not like that,and many apartments are like boxes which often screen off beautiful views like hills and mountains. Also,every road is not straight and narrow.____

    ____It was a very small market,but a very interesting one. I don't know why farmers go there to sell vegetables or why people go there to buy them because there are many more products in large supermarkets.____

    Also ,all the things sold there were very novel. In addition to fresh food,there was homemade food and many other things such as woolen blankets,quilts ,and wooden products.

    I wanted to buy some of them,but I didn't need them,so I just looked at them. It was a very exciting experience.

A. I visited a flower stand at the market.

B. Anyway,I was able to find the Farmers' Market.

C. So, to me, this American town was very impressive.

D. I decided to go early because the market is held in the morning.

E. I knew that it would take a long time to walk,but I wanted to see an American town.

F. I was attracted by the comfortable houses where they lived and the cars that they drove.

G. I think the reason is that the ones sold in the Farmers' Market are fresher and cheaper.