已知关于x的方程
.
(1)求证:无论k为何值,方程总有实数根.
(2)设
是方程
的两个根,记
,S的值能为2吗?若能,求出此时k的值;若不能,请说明理由.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6193a4b182092967b2af442f2e021afd.png)
(1)求证:无论k为何值,方程总有实数根.
(2)设
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8ce7ae90d808f05e86ea063238e4b2f9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/22ad3df8643e3ab886531be9d28a876d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/25a846776c7837c3c9da8ee4f533939f.png)
2018九年级·全国·专题练习 查看更多[3]
更新时间:2018-02-06 23:06:04
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相似题推荐
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【推荐1】利用韦达定理,解决下列问题:
(1)已知a、b是方程
的二根,求
的值.
(2)结合二元一次方程组的相关知识,解决问题:已知
和
是关于x,y的方程组
的两个不相等的实数解.问:是否存在实数k,使得
?若存在,求出的k的值,若不存在,请说明理由.
(1)已知a、b是方程
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/986aca22932d3324de0d62be9bd9b1a5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c6f4aa1fc5d666770aa3814de53bc0a9.png)
(2)结合二元一次方程组的相关知识,解决问题:已知
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac8801b911cd19405f6c763cc6a525fe.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/04ee12a3168fb5a3f52767dda74d683e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f0e4e282dd441fad095373b3dc24ef6b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d7d3c5063f3878d2457869c7909d315.png)
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【推荐2】已知,直线l:y=kx﹣k+
经过第一象限内的定点P.
![](https://img.xkw.com/dksih/QBM/2022/9/29/3076722111201280/3083246526889984/STEM/ae5d825477704bb29124e169cfb62cda.png?resizew=550)
(1)点P的坐标为______.
(2)如图1,已知点A(
,p),B(
,q),且
是关于x的方程
的两个实数根,直线AB交直线l于点B;
①求证:AB
y轴;
②若点A的横坐标为2,连接OB,若BP平分∠OBA,求k的值;
③如图2,点Q是x轴上的一动点,连接PQ,以PQ为腰作等腰△PQR(P,Q,R按逆时针顺序排列),∠QPR=120°,连接OR,请直接写出
OR+QR的最小值______.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a7ffe8515ff6183c1c7775dc6f94bdb8.png)
![](https://img.xkw.com/dksih/QBM/2022/9/29/3076722111201280/3083246526889984/STEM/ae5d825477704bb29124e169cfb62cda.png?resizew=550)
(1)点P的坐标为______.
(2)如图1,已知点A(
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c814128ea2139e33db94ea590e7c2223.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/aec19b68e3add9d5bfcc6269a1855b87.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3c516428cc0ad79391e1961fabc1d295.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0c31a610eb1f216698abb5f7369d3cf5.png)
①求证:AB
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a9bfa68259d7a331be323b2038d628a.png)
②若点A的横坐标为2,连接OB,若BP平分∠OBA,求k的值;
③如图2,点Q是x轴上的一动点,连接PQ,以PQ为腰作等腰△PQR(P,Q,R按逆时针顺序排列),∠QPR=120°,连接OR,请直接写出
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a7ffe8515ff6183c1c7775dc6f94bdb8.png)
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【推荐1】在一元二次方程中,根的判别式
通常用来判断方程实数根的个数,在实际应用中,我们也可以用根的判别式来解决部分函数的最值问题,例如:已知函数
,当
取何值时,
取最小值,最小值为多少?
解答:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ce2292541d309e0b6e4597ea6ace4467.png)
.
,即
,![](https://staticzujuan.xkw.com/quesimg/Upload/formula/76266811e652c0deffaea98d9248fcfc.png)
因此
的最小值为
,
此时
,解得
,符合题意
当
时,![](https://staticzujuan.xkw.com/quesimg/Upload/formula/237e75dd72ce6bbf337b5b82879305d2.png)
(1)已知函数
,
的最大值为多少?
(2)已知函数
,
的最小值为多少?
(3)如图,已知
,
,
是线段
上一点,
,
,
,当
为何值时,
取最小值,最小值是多少?
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f85659e819ec1fa56b8e2781d99e7422.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d22a6459bec331944130b64324a5d0ce.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d053b14c8588eee2acbbe44fc37a6886.png)
解答:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ce2292541d309e0b6e4597ea6ace4467.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0e3343bdaf2954d44deffe8b720e4cc2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4a60721558aaec802d177d23cab108e7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/df44ebc675b3a9e9ea39a0038b223e05.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/76266811e652c0deffaea98d9248fcfc.png)
因此
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d053b14c8588eee2acbbe44fc37a6886.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81fb134b2b48acc99213fff6ccfee65f.png)
此时
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e11a1a6e73633c189758c9981756da02.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/992a4903a5644de8c6fa029d8087acc1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2de0d10ef8b748d4531250c37c5d3f9e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e55aa0a20848c37c1892c567b2315e04.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/237e75dd72ce6bbf337b5b82879305d2.png)
(1)已知函数
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9dd595df18fd8ecdfd55383bccda5616.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d053b14c8588eee2acbbe44fc37a6886.png)
(2)已知函数
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/639ddf503b7da0ec15c6728fbd2192e2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d053b14c8588eee2acbbe44fc37a6886.png)
(3)如图,已知
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dd967903ed5a6f640a5b801ec8be0070.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6949cee8636079470cfdaac047d42e5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f218ca3928a627be8ef77a78d739d51f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3570a95f68349fcd9417fcda62e78e7e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac9c592bc77a4c3b913cedebcb214767.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40b319212a7e7528b053e1c7097e966.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/82f4f8e27f307a8a998a3335ba7d1bb4.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/11/1/59fab2f4-3b60-4924-b046-67feaf616968.png?resizew=125)
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【推荐2】已知关于x的方程
有两个实数根
,其中
.
(1)若
,求
的值;
(2)一次函数
的图像上有两点
,若
,求m的值;
(3)边长为整数的直角三角形,其中两直角边的长度恰好为
和
,求该直角三角形的面积.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/13c076fa7ca65b08f5b58b0284dee1cf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/215454c67e4af4fc9c179b7a37bdc3c1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/26d8dafc71b106f39f4e15442220897b.png)
(1)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7aed39f5aca78934fb383402433fe549.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fb3625894aa1bea3218ea0b8c561a18e.png)
(2)一次函数
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5b8c1212804e6d784756d48083d166e8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8e3a1467ecf286e3cadaf5aa006606f2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a8bc235df1d3cf1b65050cd1907590cf.png)
(3)边长为整数的直角三角形,其中两直角边的长度恰好为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c814128ea2139e33db94ea590e7c2223.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/aec19b68e3add9d5bfcc6269a1855b87.png)
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