题干

已知抛物线y=ax2+bx+c的开口向下,顶点坐标为(2,-3),那么该抛物线有(  )

A:最小值-3

B:最大值-3

C:最小值2

D:最大值2

上一题 下一题 0.0难度 选择题 更新时间:2019-11-11 10:23:00

答案(点此获取答案解析)

B

同类题2

阅读理解

    With freezing temperatures on the way, now it is the time to take steps to protect your four-legged family members from the cold, wet weather San Antonio winters often bring. With a few simple measures, you can ensure your pets stay happy and healthy throughout winter.

    What is the best way to protect your pets during freezing cold weather? Bring them inside. Pets (especially cats) are safer indoors. Can't have your pets inside the house? Purchase a dog house or give your pet a safe, warm place to rest.

    Certain pets are more vulnerable (易受伤害的) to cold temperatures than others. Short-haired dogs, very young or old dogs and all cats should not be left outside during winter months. Short-haired dogs may benefit from a sweater while outside.

    Pets that spend much of their day outdoors will need some extra food throughout the winter months. That's because they use up more energy trying to stay warm. A few extra kibbles probably won't hurt but make sure your pets are getting daily exercise if they're easy to gain weight. Always provide fresh, clean water regardless of the season. Check water daily and clean bowls regularly.

    Be mindful of your pets while winterizing your car. Antifreeze (防冻剂) is deadly to pets that are attracted to its sweet taste. Store all chemicals out of reach, especially if are going to bring your pets into the garage on cold nights. It is necessary to warm up the car before you head out with your pet. A warm engine can be a welcome spot for a cold cat and the noise should scare them away before your start the engine.

    San Antonio's Animal Care Services wants to remind people that the City of San Antonio has laws that protect pets from neglect, including exposure to freezing weather conditions. Animal Care Service warns that if you find any pet around being left in the freezing cold weather, you can call the City's 311 Customer Service line.

同类题5

阅读下文,回答问题。

轮椅上的歌

      ①早晨,去公园的次数多了,发现园内不仅有晨锻的人、有唱歌的人、有跳舞的人,还有许多乘坐轮椅的人,这些人虽然为数不多,却也构成了晨光中一道独特的风景。

      ②与他相识是在一道坡道上,那天我正走出公园大门,发现相邻的坡道上,一男子推着轮椅车正夹在拐角处,我正欲上前相助,他用眼光制止了我。只见他身子软软地倚着轮椅,双手紧握着车的把手,两眼注视着坡面,双脚行着,巍巍颤颤的,一寸一寸的向前挪动,额头上的青筋在微微抖动。经过约二十多分钟的艰难推进,轮椅终于拐过了转角,他长长的舒了口气,露出了胜利者的笑容。陪着他的妻子告诉我,他每天要经过无数次这样的“拼博”。正是有这样的精神,他从患病卧床不起,经半年锻练,已能推着轮椅,每天早上到公园来散步了。我在他微微的笑意中看到了生命的坚持。

      ③公园溜鸟区就在河边的竹林旁,一长排挂钩上,每天早上挤滿了各式的鸟笼,动听的鸟鸣声此起彼伏,在小河上空盘旋。我沿着公园环道快走,每次经过这儿,在一群溜鸟人中,数他的笑声最欢快。有一次问他,什么事让你天天这么快乐?他笑答,鸟欢叫我快乐!手指处,一只圆型的大鸟笼中一对美丽的小鸟正上下跳跃,欢快的鸣叫着,坐在电动轮椅上的他不时的与鸟儿呼应着。鸟友们悄悄对我说,他是位高位截瘫者,十年前一次交通事故留下了后遗症,溜完鸟他还要载着失智的老伴去散步。他的人生哲学是:笑也是一天,哭也是一天,心中充满了快乐,痛苦就进不去了!生活给了他一片阴暗,他的脸上却充满了阳光。每次看到他笑呵呵离去的背影,我从中体会到了人生的欢乐。

      ④那天,走过小树林旁,林间小径推出一辆轮椅,上面坐着个中年妇女,推车的却是位白发苍苍步履蹒跚的老太。我正纳闷,只听中年妇女对白发老太说:“阿姆,你推了这么多路吃力不?我跟你换一下,你坐着我来推你。”老太说:“我很开心,一点也不吃力。”这时跟在后面的一位中年男子对我说,老太是他的母亲,患有严重的骨质疏松,医生嘱咐要多散步、多晒太阳,但老太就不愿外出,他们夫妻俩就对老太说,按照居委会的要求,全家一起去公园做游戏,才每个礼拜天把老太“骗”了出来。我不知他们具体用了什么方法,但我从中年夫妇关注老太的目光里感受到了关爱与孝心。

      ⑤生活是一首五彩缤纷的乐曲,这些坐在轮椅上的特殊人群,用自己对生命的坚持,用自己对人生的欢乐,用自己对亲人的关爱,谱写出了一支支轮椅上的歌,在生活的乐曲中奏响了独特而又感人的旋律。