已知x=
,y=
.
(1)求代数式2x2+2y2﹣xy的值;
(2)求代数式
﹣xy的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e94c7f92e59d3935408947e09ca940d3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d46d903100e4258ef742d56efdeeb156.png)
(1)求代数式2x2+2y2﹣xy的值;
(2)求代数式
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e213d32b409476541e7f4d4481faad46.png)
21-22八年级·全国·假期作业 查看更多[2]
(已下线)第08讲 二次根式的运算-【暑假自学课】2022年新八年级数学暑假精品课(北师大版)(已下线)专题12.2 二次根式混合运算与化简求值(50题)专项训练-2022-2023学年八年级数学下册重难题型全归纳及技巧提升专项精练(苏科版)
更新时间:2022-06-21 14:35:45
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解答题-问答题
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【推荐1】在学习“乘法公式”时,七(1)班数学兴趣小组在活动课上进行了这样的操作:作两条互相垂直的线段
和
.把大正方形分成四部分(如图所示).
【观察发现】(1)请用两种不同的方法表示图形的面积,得到一个等量关系:______.
【类比操作】(2)请你作一个图形验证:
.
【延伸运用】(3)若
,图中阴影部分的面积和为29,求
的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/9/10/c9106be0-2768-4c6c-b7fd-8d66f82b18a0.png?resizew=150)
【观察发现】(1)请用两种不同的方法表示图形的面积,得到一个等量关系:______.
【类比操作】(2)请你作一个图形验证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fda5337b07e629b5bbe4b2e2151db129.png)
【延伸运用】(3)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6d4b93a76930b6545666ef7d4c11f52c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6f29d5f376c75c41ae6af0c8a8565449.png)
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【推荐1】计算:(1)12
÷3
×
;(2)(
-1)2-
×
+(
+2)×(
-2).
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1e2b3cc5d3b11fd2e271541087b1f79a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/429b921ad132643ad872712f9a7aada8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2d71c10a8e0c717542e58046332b5071.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf298f00799cbf34b4db26f5f63af92f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a7ffe8515ff6183c1c7775dc6f94bdb8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cde029ac94c601540583c64bc48c17bb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf298f00799cbf34b4db26f5f63af92f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf298f00799cbf34b4db26f5f63af92f.png)
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【推荐2】观察下列一组式的变形过程,然后回答问题:
例1:
=
=
=
=
.
例2:
=
﹣
,
=
﹣
,
=
﹣![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8b5a1a7a04d4c10e7a45714482bfb58d.png)
利用以上结论解答以下问题:
(1)
=
(2)应用上面的结论,求下列式子的值.
+
+
+…+![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3409ecfd7988e4b020d3968d630fa5d7.png)
(3)拓展提高,求下列式子的值.
+
+
+…+
例1:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b4d4014bee50f37f5f78f77eadecd06c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e0f934228b581edfc3c74f60fe329107.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/545030f510680f979b0a43bdba7583e2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6c717865916a0d68e01d032057da6889.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c34e01955f8c8fe2f0041b35d8d602a7.png)
例2:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/df8abfaf0530ee630018a76c260a81ea.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a7ffe8515ff6183c1c7775dc6f94bdb8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf298f00799cbf34b4db26f5f63af92f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2f4c446799e3745782001e471f702cfc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8b5a1a7a04d4c10e7a45714482bfb58d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a7ffe8515ff6183c1c7775dc6f94bdb8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bbaee49f5405b4f53360e312e2e5e16a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2967337e3fcb228dded64ab0c41a17e0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8b5a1a7a04d4c10e7a45714482bfb58d.png)
利用以上结论解答以下问题:
(1)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b7ceb559f12f9aa2c2b66ee21feacae5.png)
(2)应用上面的结论,求下列式子的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b4d4014bee50f37f5f78f77eadecd06c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/df8abfaf0530ee630018a76c260a81ea.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2f4c446799e3745782001e471f702cfc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3409ecfd7988e4b020d3968d630fa5d7.png)
(3)拓展提高,求下列式子的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/51a4b6a0198419df1285a6a5096dbe13.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/df376934eb787eb25742163410c82a8c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/00e662e38366380f86850f1c0a722d7d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2f448ad957e918aea7b83ce9744d81e6.png)
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【推荐1】综合运用:细心观察图形,认真分析各式,然后解答下列问题:
,
(
是
的面积);
,
(
是
的面积);
,
(
是
的面积);…
(1)请你直接写出
,
;
(2)请用含有n(n为正整数)的式子填空:
,
;
(3)在线段
、
、
、……、
中,长度为正整数的线段共有 条;
(4)我们已经知道
,因此将
分子、分母同时乘以
,分母就变成了4,请仿照这种方法求
的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bc894dd9d2528dd51fa68a4a25a01aca.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9f4f48b72329a258cf2c82273574a208.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e097c8d4c948de063796bd19f85b3a9a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9b474128b6b4fe3272d86bfb222b78ee.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9303331695244f39183f01da1cf2098d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/554a870ba0c66752f89e00ae26cc7646.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1e0bd63f55069a3bc870915010b39225.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1c65e7a4f819b27f85ee3c537a098348.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/01be303beab6857d973fe3783936bc25.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/51417ed5c9681fc9901174af61e2ec91.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6899bf9cadae2ccdb14cbc87d4f280ee.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f5ba0bc3476605c3aceb2d7555cd554f.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/11/12/f74cf362-c303-4f0a-9df4-2237d6cb51e2.png?resizew=263)
(1)请你直接写出
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/59b06c8631b08668a2ffc02f2b3382e8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ae9ad4e59d7081cf19021423a984bc29.png)
(2)请用含有n(n为正整数)的式子填空:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/20c25071879961a5670897e90f5b96e7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/04c2864e2ec3416cc4c081ac1f71a0af.png)
(3)在线段
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4195334905e2f190f958dbf5951456f8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1c76916c6ff302cf4fb4b6ace5bb3a95.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/181f7b988095b7285557491c7bb2fb5c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0b5f777a136b37ef7534744932db7239.png)
(4)我们已经知道
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/287f10de01e4d92cc91eb51bb2c10e95.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/039f6e7df4502521a84c791efb50ee20.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/941e9f1205657c88bfc1c6f1ba547280.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3882369000a3f8513b6bfcb196d6eafc.png)
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【推荐1】已知x=
,y=
求代数式x2+y2+xy-2x-2y的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5246364ca8d76ddd707a001fe98cbb5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fbece4ff65913b33b9acee288deb30f2.png)
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【推荐2】已知a=
+1,b=
﹣1,求下列各式的值:
(1)a2﹣2ab+b2,
(2)a2﹣b2.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf298f00799cbf34b4db26f5f63af92f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf298f00799cbf34b4db26f5f63af92f.png)
(1)a2﹣2ab+b2,
(2)a2﹣b2.
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