用户名 密码
&当前位置:&&&
& 题目详情
可以插入公式啦！&我知道了&
（;乐山）已知二次函数y=ax2+bx+c的图象如图所示，记m=|a-b+c|+|2a+b+c|，n=|a+b+c|+|2a-b-c|．则下列选项正确的是（　　）
D．m、n的大小关系不能确定
正在获取……
(注：此处只显示部分答案，可能存在乱码，查看完整答案不会有乱码。)
解：∵抛物线开口向下，
∴a＜0，
∵对称轴在y轴右边，
∴b＞0，
∵抛物线经过原点，
∴c=0，
∴a-b+c＜0；
∵x=1时，y＞0，
∴a+b+c＞0，
∵c=0，
∴a+b＞0；
（1）当对称轴x=-≤1时，
2a+b≥0，
m=|a-b+c|+|2a+b+c|
=b-a+2a+b
=2b+a
n=|a+b+c|+|2a-b-c|
=a+b+（b-2a）
=2b-a
∵a＜0，
∴2b+a＜2b-a，
∴m＜n．
（2）当对称轴x=-＞1时，
2a+b＜0，
m=|a-b+c|+|2a+b+c|
=b-a-（2a+b）
=-3a
n=|a+b+c|+|2a-b-c|
=a+b+（b-2a）
=2b-a
m-n=（-3a）-（2b-a）
=-2（a+b）
∵a+b＞0，
∴-2（a+b）＜0，
∴m＜n．
综上，可得m＜n．
故选：A．
分析：首先根据抛物线开口向下，可得a＜0；然后根据对称轴在y轴右边，可得b＞0；再根据抛物线经过原点，可得c=0；再根据x=1时，y＞0，判断出a+b+c＞0，a＞-b；最后分两种情况讨论：①当对称轴x=-≤1时；②当对称轴x=- …(点击上面的蓝色链接“查看完整答案与解析”字样可以查看完整答案)
合肥网友&&&
当对称轴x=-
＞1时， 2a+b＜0， 错
无锡网友&&&
当对称轴x=-2a
≤1时， 2a+b≥0，错了2a+b应是小于等于0
银川网友&&&
x=1时为什么y&0，如果1在右边交点的右侧呢
合肥网友&&&
为什么x=1时a+b+c&o
晋城网友&&&
晋城网友&&&
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皖ICP备1101372号334被浏览40727分享邀请回答int t = a;
这才是正确做法（或者使用swap我看到了题目有算法两个字(￣_,￣ )我的内心毫无波动，向题主丢出了 （）与
（）19247 条评论分享收藏感谢收起294 条评论分享收藏感谢收起查看更多回答Scan report for http://share.v./index.php?c=share&a=index&title=%23QQ%E9%A3%9E%E8%BD%A6%E6%8A%BD%E5%A5%96%E7%A7%92%E6%9D%80%E5%99%A8%E5%85%8D%E8%B4%B9%E4%BA%86%23+%23%E6%8E%A8%E8%8D%90%E6%94%B6%E5%90%AC%23%20%E2%86%92%E3%80%8E%40tangyanhong%E3%80%8F%E4%B8%BA%E4%BA%86%E6%84%9F%E8%B0%A2%E5%B9%BF%E5%A4%A7%E7%94%A8%E6%88%B7%E5%AF%B9%E6%9C%AC%E8%BD%AF%E4%BB%B6%E7%9A%84%E4%BF%A1%E4%BB%BB%EF%BC%8C%E4%BD%9C%E8%80%85%E5%86%B3%E5%AE%9A%E6%8E%A8%E5%87%BA%E2%80%9C%E6%8A%BD%E5%A5%96%E7%A7%92%E6%9D%80%E5%99%A8%E2%80%9D%E7%9A%84%E5%85%8D%E8%B4%B9%E7%89%88%E6%9C%AC%EF%BC%81%E6%83%B3%E6%8B%A5%E6%9C%89%E6%B0%B8%E4%B9%85A%E8%BD%A6%E5%90%97%EF%BC%9F%E6%83%B3%E6%8B%A5%E6%9C%89%E7%BB%9D%E7%89%88%E8%A3%85%E5%A4%87%E5%90%97%EF%BC%9F%E9%82%A3%E5%B0%B1%E5%BF%AB%E6%9D%A5%E4%B8%8B%E8%BD%BD%3Ahttp%3A%2F%%2F++++++++%23%E5%88%86%E4%BA%AB%E8%A7%86%E9%A2%91%23&url=http%3A%2F%%2Fprograms%2Fview%2FTs-W4CzEZZI%2F%3FresourceId%3D_02_99&appkey=&site=&pic= at
12:59:59 UTC - VirusTotal
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Final URL after redirects
http://share.v./index.php?c=share&a=index&title=%23QQ%E9%A3%9E%E8%BD%A6%E6%8A%BD%E5%A5%96%E7%A7%92%E6%9D%80%E5%99%A8%E5%85%8D%E8%B4%B9%E4%BA%86%23+%23%E6%8E%A8%E8%8D%90%E6%94%B6%E5%90%AC%23%20%E2%86%92%E3%80%8E%40tangyanhong%E3%80%8F%E4%B8%BA%E4%BA%86%E6%84%9F%E8%B0%A2%E5%B9%BF%E5%A4%A7%E7%94%A8%E6%88%B7%E5%AF%B9%E6%9C%AC%E8%BD%AF%E4%BB%B6%E7%9A%84%E4%BF%A1%E4%BB%BB%EF%BC%8C%E4%BD%9C%E8%80%85%E5%86%B3%E5%AE%9A%E6%8E%A8%E5%87%BA%E2%80%9C%E6%8A%BD%E5%A5%96%E7%A7%92%E6%9D%80%E5%99%A8%E2%80%9D%E7%9A%84%E5%85%8D%E8%B4%B9%E7%89%88%E6%9C%AC%EF%BC%81%E6%83%B3%E6%8B%A5%E6%9C%89%E6%B0%B8%E4%B9%85A%E8%BD%A6%E5%90%97%EF%BC%9F%E6%83%B3%E6%8B%A5%E6%9C%89%E7%BB%9D%E7%89%88%E8%A3%85%E5%A4%87%E5%90%97%EF%BC%9F%E9%82%A3%E5%B0%B1%E5%BF%AB%E6%9D%A5%E4%B8%8B%E8%BD%BD%3Ahttp%3A%2F%%2F++++++++%23%E5%88%86%E4%BA%AB%E8%A7%86%E9%A2%91%23&url=http%3A%2F%%2Fprograms%2Fview%2FTs-W4CzEZZI%2F%3FresourceId%3D_02_99&appkey=&site=&pic=
IP address resolution
58.251.139.142
HTTP Response code
HTTP Response headers
content-length: 8238
x-powered-by: PHP/5.2.12
set-cookie: __hash__=899d4dd0bfade8b5277c8cbab57a6ca2; expires=Tue, 27-Oct-:00 GMT; path=/; domain=share.v.
vary: Accept-Encoding
server: nginx/1.5.7
connection: keep-alive
date: Mon, 26 Oct :00 GMT
p3p: CP=CURa ADMa DEVa PSAo PSDo OUR BUS UNI PUR INT DEM STA PRE COM NAV OTC NOI DSP COR
content-type: text/ charset=utf-8
Response content SHA256
f00d35d323dd08db35c54ccffd8a7c4910
Scanning engine details
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