名校
1 . 根据多元微分求条件极值理论,要求二元函数
在约束条件
的可能极值点,首先构造出一个拉格朗日辅助函数
,其中
为拉格朗日系数.分别对
中的
部分求导,并使之为0,得到三个方程组,如下:
,解此方程组,得出解
,就是二元函数
在约束条件
的可能极值点.
的值代入到
中即为极值.
补充说明:【例】求函数
关于变量
的导数.即:将变量
当做常数,即:
,下标加上
,代表对自变量x进行求导.即拉格朗日乘数法方程组之中的
表示分别对
进行求导.
(1)求函数
关于变量
的导数并求当
处的导数值.
(2)利用拉格朗日乘数法求:设实数
满足
,求
的最大值.
(3)①若
为实数,且
,证明:
.
②设
,求
的最小值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e4a1d0dba29a77dd111efcde543d6c1f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bc4c14935585e8fa61d032730867d771.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/67b6f154c6b2de5695eb1807b98c2c63.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/df64046e91b047037f19e4032e3b6de3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/809615d1f91508e2c6c0cda7e592c479.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/244021f826099b18e31af1143597bba2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/eb5be11a5e6aaf00b2833930b198b4cf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0203b006524305c3d8ee0b6c34cd872b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e4a1d0dba29a77dd111efcde543d6c1f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bc4c14935585e8fa61d032730867d771.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9b0fffbec1fe851795dfdd448bf0d165.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f1c3c1ed4fb65ab9505ad8078d8d0fb5.png)
补充说明:【例】求函数
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0d7ca0caa9933b7afd4bed2683140a07.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d053b14c8588eee2acbbe44fc37a6886.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/aebdee8d81b048b5aa520f7e8ba56ff2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5a1e15a54c6122c695239107dd0901bc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/244021f826099b18e31af1143597bba2.png)
(1)求函数
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9b3d9ab2fcf15b94f33cb64f84ed906c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d053b14c8588eee2acbbe44fc37a6886.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9b384412acba251d87902ab928902f16.png)
(2)利用拉格朗日乘数法求:设实数
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9b0fffbec1fe851795dfdd448bf0d165.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6c45d8122b61de13875003d00c002c5b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/de725a9fc66f67abbe0015131846a648.png)
(3)①若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1a14c388e1e2e5a2ff1ccf6caffbee0d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bd24c686fbaaa68705d654b880481ffe.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e778f95c72fec00bfbbc63e6dfd0c460.png)
②设
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/497d269c30eec393e3f0e877ddbe2983.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ade042c085bbad8aeaf111b9f4c33408.png)
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解题方法
2 . (1)解不等式组
;
(2)若不等式
对
恒成立,求实数
的取值范围.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0fabc69ba02793ce682105806a7c4b42.png)
(2)若不等式
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cce4e46b4286bd43e3ad3312ece637c6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9e541ea2f855f981c96207070683d388.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6936d370d6a238a608ca56f87198de.png)
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3 . 已知方程组
,对此方程组的每一组正实数解
,其中
,都存在正实数
,且满足
,则
的最大值是________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f53478749934135785de9d8e31aa04df.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a2322e25b48e7f4263f0c02aaabfdb74.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/62f78f8accdac9fc8008fe363e3eabff.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a1c7a2e2cb4e8449a4b646e62f3b9a86.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
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解题方法
4 . 设
.
(1)若不等式
对一切实数x恒成立,求实数m的取值范围;
(2)在(1)的条件下,求
的最小值;
(3)解关于x的不等式
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6ab21274f0a4c68000ffd70abbc0b64d.png)
(1)若不等式
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1e59bb4bf2e0698d876cf815362b3658.png)
(2)在(1)的条件下,求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b9aaa48c24bcd35f215d27adcb5d00f1.png)
(3)解关于x的不等式
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4c0243e9dd6621e4d7c2eccc1bc3caf6.png)
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2024-04-23更新
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2卷引用:广东省河源市河源中学2023-2024学年高一上学期第一次段考数学试题
名校
解题方法
5 . (1)已知
,若对任意
,都有
,求
的最小值;
(2)解关于x的不等式
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/709c7121314576276e4a561aca9558ee.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4921923069c4f38a0af1ff8637e35b3c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/34a4a82f38d05d5ee55736cce9cb4d67.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/20d6fc9b90f370fbb27552876b650f8f.png)
(2)解关于x的不等式
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2d4bfa16454ef318f602eae03ad32ee0.png)
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6 . 已知函数
,其中
.
(1)当
时,求函数
,
的最小值;
(2)解关于
不等式
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7907e8be70c47759be0e604205602e7f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/94440d3e4c073f94f2b266ff99d50e74.png)
(1)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0b550ee821ee1838384835e81fc34b67.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dc7449f60f359412bf73415c684cb636.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/790daaa89fc9d093f45023becf765697.png)
(2)解关于
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2496a3da65447ec582d9d92a45db8a52.png)
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解题方法
7 . 设函数
,
.
(1)解关于x的不等式
;
(2)当
时,不等式
恒成立,求a的取值范围.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1ede4a660ea4ec1bac8834a388f54a69.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/10bbdef421c976962a270a2beabbad91.png)
(1)解关于x的不等式
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a71baf6217604517fd98fa97d0f55b43.png)
(2)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4921923069c4f38a0af1ff8637e35b3c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5967cc62862986840af4dd29df4bcc41.png)
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解题方法
8 . 已知函数![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1bc80dbbe84c6eaf2310fc863c86532c.png)
(1)解关于x的不等式:
;
(2)若
(
),求
的最小值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1bc80dbbe84c6eaf2310fc863c86532c.png)
(1)解关于x的不等式:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6c2e0bb6d63b7bcaee92a470d58cc399.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/aba934874cc9f2ab272fdff67ea23bf6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2958030ec9d7543dda1f529593a915e2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ce460941cf3ff54ccb6aec5085689a91.png)
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2024-01-24更新
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3卷引用:江苏省淮安市2023-2024学年高一上学期期末调研测试数学试题
名校
解题方法
9 . 已知函数
.
(1)当
时,求关于
的不等式
的解集;
(2)
,关于
的方程
在
总有两个不同实数解,求实数
的取值范围;
(3)若
在区间
上恒成立,求实数
的取值范围.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1ede4a660ea4ec1bac8834a388f54a69.png)
(1)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8e258ab9e600435b37465092243d99f6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1c73a98c1b3504e09bfbe0db849b0d24.png)
(2)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a4abca1cd298c31bf8c0babfea7074d4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60c885198ab1a7a342aa35ced7461b16.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac4cbc7b067862a3d9c6789b392fc068.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c94bb12cee76221e13f9ef955b0aab1.png)
(3)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5ec0a04d44656bd8b58d19afabbf235.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e5d6243e93c41978871cb23d8e66148d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6936d370d6a238a608ca56f87198de.png)
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2024-01-01更新
|
416次组卷
|
2卷引用:黑龙江省齐齐哈尔市克东县第一中学2023-2024学年高一上学期12月月考数学试卷
解题方法
10 . 已知二次函数
,其中
.
(1)若
,解关于
的不等式
;
(2)若
且不等式
对一切实数
恒成立,求
的最小值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b1bd0587f5d6a3b5db9e4a93e0dbc0ef.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f3eb9b6fe8959ae9e71e857b6d6fed49.png)
(1)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d0ea451f7feb1e03c1e31086e7db461.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/018857ec6e498113b3b12a730d9313da.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c6a46e678bf9d2df5ad4c782b3dc22f5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/22e38c541dec8fce1d26886e5ef7d21f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c15d40a6f559b5d1c71216768c10445f.png)
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