题干

设F1、F2是双曲线
x
2
a
2
-
y
2
b
2
=1
(a>0,b>0)的左、右焦点,P是双曲线右支上一点,满足(OP+OF2·PF2=0(O为坐标原点),且3|PF1|=4|PF2|,则双曲线的离心率为____
上一题 下一题 0.0难度 选择题 更新时间:2019-08-05 09:43:51

答案(点此获取答案解析)

5

同类题1

阅读下文,回答问题

父爱不矮小

    ①第一次发现自己个子矮,是在她12岁那年。

    ②“六一”前夕,学校照例要举办一台联欢会。选节目那天,她哭着回了家。老师把她在几个女孩子之间换来换去之后,无奈又失望地摇摇头。比同班的女孩子矮了半头的她站在舞蹈队伍里显得极不协调,伙伴们已长成婷婷的天鹅,而她依然是只瘦弱的小鸟。

    ③她哭着问妈妈,为什么别人都长高了,就她不长。妈妈没意识到落选的事对女儿的伤害,笑着摸了摸她的头说:“你要是随了妈就好了,谁让你随了你爸呢。”一旁的父亲局促地搓搓手,没有说话,转身走了。从那天起,她才注意到父亲竟是如此矮小。也是从那天起,她在心里怨上了父亲。

    ④那个不愉快的儿童节过后不久,她的小学时代结束了。曾经向往的中学生活并没有想象中的愉快。在这所小镇唯一的中学里,她和父亲经常被别人一同提起,因为父亲是这所学校的语文老师。有时,她正在操场上和同学快乐地打球,身边走过的老师或同学会说,她长得真像她父亲。这时,快乐会瞬间飞远。语文课上,她的作文被老师夸奖,同学们的羡慕和赞许会让她充满欢喜。下课后,老师夸她:“这丫头好文采,随你父亲。”最后这一句,让她心里的欢喜打了折扣。她挺挺娇小的身体,委屈着,为什么我要像父亲。

    ⑤蔷薇花开了落,落了开,她也花一样长得清纯,个子更显得玲珑娇小。她考进城里的大学后,除却离家的新鲜,还有个小小的快乐,那就是耳边不会再有人说她像父亲了。一日,她被同学从操场上叫回宿舍,是父亲来了。(A)他似乎并未察觉她的不快,笑着递给她两大包饼干,还有两本她喜爱的文学书。临走时,父亲又回头说:“丫头,记着吃饼干啊,每天都要吃。”她望着父亲矮小的背影怨着:“哪里没有卖饼干的?不要再给我送了。”

    ⑥假期回家。一进门父亲就问:“丫头,饼干吃完了吗?”说着又抱出几袋一样的饼干。“您就不知道换个牌子呀?干吗让我天天吃这个?”母亲望望父亲说:“丫头,你爸听朋友说有种赖氨酸饼干,孩子吃了能长高个,他就跑到城里四处找。这不,好容易才买到,立刻就给你送去了。”她的心里倏地疼了一下。(B)以后的日子里,她吃着父亲送来的饼干,打着球,似乎真的长高了一些,婷婷的,像一株春日里的翠竹。

    ⑦又是蔷薇花满院飘香的季节,她带回一个高大俊朗的男孩。忙忙碌碌的父亲在男孩的身边显得更加矮小,可父亲脸上的欢喜就像阳光下的蔷薇花,笑盈盈地开满了小小的院子。

    ⑧黄昏,她送男孩出门。男孩很认真地对她说:“你爸真好。他对我说,我把女儿交给你,以后你们如果吵架了,你可以怨她懒,可以说她娇气,但是,你永远都不许嫌她矮。”

    ⑨瞬间,她的泪扑簌簌地挂满了脸颊。莹莹的泪光中回望,缤纷绚烂的蔷薇花旁,父亲的身影被一抹夕阳拉得修长……

同类题3

阅读理解

    After opening the world's first commercial Direct Air Capture plant(直接空气捕集工厂)designed to pull CO2 out of the air, Swiss company Climeworks is now trying to create the world's first “negative emission(负排放)” power plant.

    An international team of scientists has been working on a way to turn captured CO2 into minerals. The project is called CarFix. Experts capture the gas, put it into water and send it to more than 700 meters underground. There the CO2 on contact with a special kind of rock forms into a mineral.

    “Our results show that between 95 and 98 percent of the CO2, sent underground was mineralized over the period of less than two years, which is amazingly fast,” says lead author of the CarFix project, Dr. Juerg Matter. Before this discovery it was thought that this mineralization could take hundreds to thousands of years.

    The DAC technology can collect CO2 from the atmosphere and then store it underground or sell it to business needing the gas. For example, customers can use it in drinks. And the first plant in Zurich is supplying the captured CO2 to a nearby greenhouse to “feed” vegetables. By using the company's CO2 the customers can reduce their carbon mission as well as lower their dependence on energy.

    A 2015 study suggested that before the CarFix project, experts could collect CO2, but they didn't have a large-scale(大规模的)method to safely treat it.

    Combining Climeworks' DAC technology with the CarFix mineralization process they will be able to create a system. This system doesn't put additional carbon back into the atmosphere. Actually it is carbon negative.

    “The economic cost of applying this kind of carbon capture technology on a large-scale is not particularly practical now, but for the first time we are seeing a realistic and effective system,” says Christoph Gebald CEO of Climeworks.