题干

如果把分式
x
y
x
+
y
中的x和y都扩大2倍,则分式的值(  )

A:扩大4倍

B:扩大2倍

C:不变

D:缩小2倍

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答案(点此获取答案解析)

B

同类题1

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妹妹扮演的角色

    ①为了募捐,学校准备排练一部短话剧。告示一贴出,妹妹便热情万丈地去报名当演员。可是定角色那天,妹妹回家后一脸冰霜,嘴唇紧闭。“你被选上了吗?”我们小心翼翼地问她。

    ②“是。”她丢给我们一个字。“那你为什么不开心?”我壮着胆子问。

    ③“因为我的角色!”

    ④短话剧中只有4个人物:父亲、母亲、女儿和儿子。 “你的角色是什么?”

    ⑤“他们让我演狗!”说完,妹妹转身奔上楼,剩下我们面面相觑。妹妹有幸扮演“人类最忠实的朋友”,全家不知该恭喜她,还是安慰她。饭后爸爸和妹妹谈了很久。

    ⑥总之,妹妹没有退出,她积极参加每次排练。我们都纳闷:一只狗有什么可排练的?但妹妹却练得很投入,还买了一副护膝。据说这样她在舞台上爬时,膝盖就不会疼了。妹妹还告诉我们,她的动物角色名叫“豆豆”。我注意到,每次排练归来,妹妹眼里都闪着兴奋的光芒。

   ⑦ 演出那天,我翻开节目单,找到妹妹的名字:“甄妮——豆豆(狗)”。偷偷环视四周,整个礼堂都坐满了,其中有很多熟人和朋友,我赶紧往椅子里缩了缩。有一个演狗的妹妹,毕竟不是很有面子的事。幸好,灯光转暗,演出开始了。

    ⑧先出场的是“父亲”,他在舞台正中的沙发上坐下,召集家人。接着“母亲”“女儿”和“儿子”先后出场。在一家人的谈话声中,妹妹穿着一套黄色的、毛茸茸的狗道具,手脚并用地爬进场。

    ⑨但这不是简单地爬,“豆豆(妹妹)”蹦蹦跳跳、摇头摆尾地跑进客厅,她先在地毯上伸个懒腰,然后才在沙发旁安顿下来,开始呼呼大睡。一连串动作,惟妙惟肖。很多观众也注意到了,四周传来轻轻的笑声。

    ⑩接下来,剧中的父亲开始给全家讲故事。他刚说到“夜晚,万籁俱寂,就连老鼠……”“豆豆”突然从睡梦中惊醒,机警地四下张望,仿佛在说:“老鼠?哪儿有老鼠?”神情和我家的小狗一模一样。我用手掩着嘴强忍住笑。

    ⑪男主角继续讲:“突然,轻微的响声从屋顶传来……”昏昏欲睡的“豆豆”又一次惊醒,好像察觉到异样,仰视屋顶,喉咙里发出呜呜的低吼。太逼真了!妹妹一定费尽了心思。很明显,这时候的观众已不再注意主角们的对白,几百双眼睛全盯着妹妹。妹妹幽默精湛的表演使得台下的笑声此起彼伏。

    ⑫那晚,妹妹的角色没有一句台词,却抓住了所有观众的心。后来,妹妹说让她改变态度的是爸爸的一句话:“如果你用演主角的态度去演一只狗,狗也会成为主角。”

    ⑬40年后,那句话我仍然记忆犹新。命运赋予我们不同的角色,与其怨天尤人,不如全力以赴。再小的角色也有可能变成主角。

同类题4

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    If you want to live longer and lower the risk of heart disease, a move to the mountains may help. Research by scientists in Greece shows that living in the mountains is good for the heart and longevity(长寿). People living at higher altitude(海拔) have lower possibility of dying from heart disease than those closer to sea level, even if they have factors that could increase their risk. "Residence in mountainous areas seems to have a 'protective effect' from heart disease," said Dr Nikos Baibas of the University of Athens. He and his colleagues suspect that the increased exercise from walking up mountainous area gives the heart a good workout and enables it to cope with lower levels of oxygen.

    Researchers studied the health records and death rates of 1,150 Greeks who lived in three villages near Athens over 15 years. One village was 1,000 meters above sea level and the other two were in low-lying areas. Although men and women living in the mountainous village had higher blood pressure rates and other risk factors than people in the other villages, they had a lower rate of death from heart disease and other causes after a fifteen year follow-up." The contrast was more evident among men than among women," Baibas added in a report in the Journal of Epidemiology and Community Health. Heart disease is one of the world's top killers. Smoking, high blood pressure, raised cholesterol levels, being overweight and a family history of the illness increase the possibility of developing the disease.