已知a+b=7,ab=11,求代数式
的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6992aac725a392314baaeb64a2e6217b.png)
更新时间:2021-02-18 20:25:42
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解答题-计算题
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适中
(0.65)
【推荐1】化简或求值:
(1)
;
(2)
;
(3)先化简,再求值,
,其中
,
.
(1)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/181a01d4cafdb23d059225ebac3c141a.png)
(2)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/11c26366ef962ad5e104df661617d90d.png)
(3)先化简,再求值,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ecb8fe7fead437cc05328ac33553d729.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6b108ab31cc093f03cf48ad65429889e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dc64eaf4cd6737b000b28f1fcdd16c4b.png)
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解答题-计算题
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适中
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【推荐2】先化简,再求值:6x2-[3xy2-2(3xy2-1)+6x2],其中(x-4)2+|2y+1|=0.
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解答题-问答题
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名校
【推荐1】阅读理解.
因为
, ①
因为
②
所以由①得:
, 由②得:![](https://staticzujuan.xkw.com/quesimg/Upload/formula/05649797b4796bcc7a3649744dd503a7.png)
所以![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f8e4e895b9b24d3c49b0e3c27cde0c86.png)
试根据上面公式的变形解答下列问题:
(1)已知
,则下列等式成立的是( )
①
; ②
; ③
; ④
;
A.①; B.①②; C.①②③; D.①②③④;
(2)已知
,求下列代数式的值:
①
; ②
;③
.
因为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3b31452b3beb8cfafeed5064f7c9745a.png)
因为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/89382a10bed9ab94bbcbff4687b6394e.png)
所以由①得:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/539da7f219d2dcad91cdf176eba64179.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/05649797b4796bcc7a3649744dd503a7.png)
所以
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f8e4e895b9b24d3c49b0e3c27cde0c86.png)
试根据上面公式的变形解答下列问题:
(1)已知
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fd13e8b5914af55dad0f3946527a46bf.png)
①
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/61e585b15b938a26204a61d93ee31fd9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/908d80eef6c5b0a911052ddc69283652.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/215f7739cebde0f4a348fc957acb5c92.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/33f27550aedf70ff6b00f2e016906493.png)
A.①; B.①②; C.①②③; D.①②③④;
(2)已知
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e03bc2dbe8ae2bba9a2a8794d9913443.png)
①
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/00cc039eeaca54a5b5f4228f7e0c18bd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/030bc245658c4ac44ea9e710f502991b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e3527b502026133d4fffdeb08245f272.png)
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解答题-计算题
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适中
(0.65)
【推荐2】【知识生成】我们已经知道,通过计算几何图形的面积可以表示一些代数恒等式.例如图1可以得到
,基于此,请解答下列问题:
【直接应用】(1)若
,
,求
的值;
【类比应用】(2)若
,求
的值;
以下是亮亮同学的解法:
解:∵
,
∴
,
∵
,
∴
.
爱动脑筋的琪琪同学看了亮亮同学的解法后,灵机一动说到:“我还有其它不同的解法.”请你结合材料,类比第(1)题进行解答;
【知识迁移】(3)两块形状大小都相同的直角梯形(![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4f82beaeb58778dff70c879f25bb0083.png)
)如图2所示放置,其中A、
、
三点在同一直线上,连接
、
.若
,每一个直角梯形的面积为
,且下底是上底的2倍,求
与
的面积之和.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8f88bd30cd20a8b2b2f8d3019674f0af.png)
【直接应用】(1)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0be22a11d63325bcd90daaecfcc60636.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/71a120e118263f6b9fde8054e1a57479.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/29ebc856291255f2d4a6c20b982a2442.png)
【类比应用】(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a04e94b6d98c7665c1a890617d36828d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/89fca995114850b388ad542c01ea9562.png)
以下是亮亮同学的解法:
解:∵
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b0cedcbead8f4386537c216b775cb7b5.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/480c4724a06a12c0ffb7400308133c31.png)
∵
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8a37f95c4d9a120d3c3855664faaba54.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/022cdda16f7f5ab39a3fc57d8a4203f6.png)
爱动脑筋的琪琪同学看了亮亮同学的解法后,灵机一动说到:“我还有其它不同的解法.”请你结合材料,类比第(1)题进行解答;
【知识迁移】(3)两块形状大小都相同的直角梯形(
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4f82beaeb58778dff70c879f25bb0083.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8f3ef00c6b6ca26c0ff1b8271b532140.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4cae70b8a9d2d2e96dea62c00ced04b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/973c1938b9dc482e164e431b1129cc89.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/93ddce6dd8d5630af4c38cf4010dbefa.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/372629a8666de1e9bac3e7daadcac7b6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a54de7e539151a11b1aeed986057c6b5.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/11/20/588e4851-7175-404b-9ac9-aa5123656407.png?resizew=407)
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