猪猪水梅
幼苗
共回答了18个问题采纳率:94.4% 举报
设
![](https://img.yulucn.com/upload/a/58/a58b4326fb80d9ad4a8da39ed61747e5_thumb.jpg)
为抛物线
![](https://img.yulucn.com/upload/a/41/a41e0c9a8d4c9862dee6b33c0452adfa_thumb.jpg)
(
![](https://img.yulucn.com/upload/c/3e/c3e5d3db878ca71ea731a4d820732d42_thumb.jpg)
)的焦点,
![](https://img.yulucn.com/upload/e/80/e80d3e5a08f7121c600aa599b1d9c094_thumb.jpg)
为该抛物线上三点,若
![](https://img.yulucn.com/upload/e/97/e9783b27c2b6a34fadfabe891dc40cf9_thumb.jpg)
,且
(Ⅰ)求抛物线
![](https://img.yulucn.com/upload/0/e8/0e81496af6d5c1bc02e1efab746982f6_thumb.jpg)
的方程;
(Ⅱ)
![](https://img.yulucn.com/upload/b/7e/b7e4d4d73ec7cdc17dff15a0453cbe5d_thumb.jpg)
点的坐标为(
![](https://img.yulucn.com/upload/e/1d/e1d5d6ced087129d01a9dd1245f5840d_thumb.jpg)
,
![](https://img.yulucn.com/upload/d/f4/df4f466db675015ca12fce7ecff55d74_thumb.jpg)
)其中
![](https://img.yulucn.com/upload/0/07/007a62dcef7f490818ce334996630743_thumb.jpg)
,过点F作斜率为
![](https://img.yulucn.com/upload/8/d9/8d9f4224d634f8a74150af8b36b37524_thumb.jpg)
的直线与抛物线交于
![](https://img.yulucn.com/upload/7/ad/7ad1086bec86c81ee02955822c4e2ef3_thumb.jpg)
、
![](https://img.yulucn.com/upload/5/6c/56c30f14af6b5f49dabecfdb1255572c_thumb.jpg)
两点,
![](https://img.yulucn.com/upload/7/ad/7ad1086bec86c81ee02955822c4e2ef3_thumb.jpg)
、
![](https://img.yulucn.com/upload/5/6c/56c30f14af6b5f49dabecfdb1255572c_thumb.jpg)
两点的横坐标均不为
![](https://img.yulucn.com/upload/e/1d/e1d5d6ced087129d01a9dd1245f5840d_thumb.jpg)
,连结
![](https://img.yulucn.com/upload/9/f0/9f0c2453326610483b697883e4453601_thumb.jpg)
、
![](https://img.yulucn.com/upload/e/91/e910e0201f9942ed778e9ac8a3d2aeed_thumb.jpg)
并延长交抛物线于
![](https://img.yulucn.com/upload/e/ae/eae8ad653631a5ac2b17ea9a092a8f86_thumb.jpg)
、
![](https://img.yulucn.com/upload/1/14/1141cee2ab2699e99e8f4e071df46fd5_thumb.jpg)
两点,设直线
![](https://img.yulucn.com/upload/3/d2/3d2337665b5e34c131e653cce7ee9b8e_thumb.jpg)
的斜率为
![](https://img.yulucn.com/upload/5/7d/57d6c2499f610a58d18a1151d36a5c69_thumb.jpg)
.若
![](https://img.yulucn.com/upload/7/d7/7d7010b2f8fe900b77cba56810e66141_thumb.jpg)
,求
![](https://img.yulucn.com/upload/e/1d/e1d5d6ced087129d01a9dd1245f5840d_thumb.jpg)
的值.
(Ⅰ)
![](https://img.yulucn.com/upload/1/33/133ae028db4cce6c2f35857b0fc8f4ea_thumb.jpg)
(Ⅱ)
![](https://img.yulucn.com/upload/c/85/c85db8c6c2eb5124a0924783276a327f_thumb.jpg)
.
试题分析:(Ⅰ)利用向量和为0得到三点横坐标和的关系,结合三个向量的模为6得到
![](https://img.yulucn.com/upload/8/39/8399683a807d2be06c0d07b030dd6760_thumb.jpg)
的值,求出抛物线的方程;(Ⅱ)通过点坐标表示斜率,设直线方程,联立直线方程与抛物线方程利用韦达定理得到关于
![](https://img.yulucn.com/upload/0/77/0770de59cc1c47996d642b42b215f704_thumb.jpg)
的方程,计算得到
![](https://img.yulucn.com/upload/e/1d/e1d5d6ced087129d01a9dd1245f5840d_thumb.jpg)
.
(Ⅰ)设
则
![](https://img.yulucn.com/upload/c/36/c366047c4d55e97ea65b6c69b5d73942_thumb.jpg)
2分
![](https://img.yulucn.com/upload/9/17/917cdc681ab0f76bf7e62a6d9ff2f1af_thumb.jpg)
,所以
![](https://img.yulucn.com/upload/d/39/d39cda9fc218b342b97d4cdc02e3ee67_thumb.jpg)
.
![](https://img.yulucn.com/upload/f/00/f00338a8793530112b5eb8caa0e7da06_thumb.jpg)
4分
所以
![](https://img.yulucn.com/upload/7/44/744b3caebdf97bc83fc1505bfdefb29d_thumb.jpg)
,所以
![](https://img.yulucn.com/upload/1/33/133ae028db4cce6c2f35857b0fc8f4ea_thumb.jpg)
为所求. 5分
(Ⅱ)设
则
![](https://img.yulucn.com/upload/d/b7/db736d537c8904a50eefb25e0fe8293b_thumb.jpg)
,同理
![](https://img.yulucn.com/upload/6/65/665ad4e0c15633e7c1aa9887f5f4f69c_thumb.jpg)
7分
所以
设AC所在直线方程为
![](https://img.yulucn.com/upload/d/b6/db62bb0e2158cf5d3afa5ab7f73e98b4_thumb.jpg)
,
联立
![](https://img.yulucn.com/upload/1/33/133ae028db4cce6c2f35857b0fc8f4ea_thumb.jpg)
得,
![](https://img.yulucn.com/upload/4/e2/4e2c7249b4eca8751862a9adc9665043_thumb.jpg)
,所以
![](https://img.yulucn.com/upload/6/a3/6a3f8f2e22afea6cb2987409a357a7ba_thumb.jpg)
, 9分
同理
![](https://img.yulucn.com/upload/2/f2/2f29513d545796426e4a3ebceebd2651_thumb.jpg)
,
![](https://img.yulucn.com/upload/4/33/4336fc460f07047c8d940ce994d8d81d_thumb.jpg)
.
所以
![](https://img.yulucn.com/upload/c/73/c732e6e88a7bb7d462e1b12fa36f161f_thumb.jpg)
11分
设AB所在直线方程为
![](https://img.yulucn.com/upload/e/49/e49f2843d7bab4644e736cc8ea1ff791_thumb.jpg)
,联立
![](https://img.yulucn.com/upload/1/33/133ae028db4cce6c2f35857b0fc8f4ea_thumb.jpg)
得,
1年前
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