阅读理解:我们知道
=3,
=7,反过来,得到3=
,7=
,由此我们可以将式子9
和4
进行化简,即9
=
=
;4
=
=
.
依照上面的方法,化简下列各式:
(1)3
;(2)5
;(3)12
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5a5d753c164ef76c3c3fffbcaeeb5d3a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/89b7dc7a19a5803081181372e200d8bb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5a5d753c164ef76c3c3fffbcaeeb5d3a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/89b7dc7a19a5803081181372e200d8bb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fe22465a310e6ca225a39ab9d50769c2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1411e66402359355af5ef24dde907b08.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fe22465a310e6ca225a39ab9d50769c2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f0accf88259f120d36f4a4237a7402a7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a7ffe8515ff6183c1c7775dc6f94bdb8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1411e66402359355af5ef24dde907b08.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/554b63a4ad25702aae06bc1e2f9e6b12.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf298f00799cbf34b4db26f5f63af92f.png)
依照上面的方法,化简下列各式:
(1)3
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1cf33c54dac0b9fc5d1800e5df36619b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7173e8a9675a7d8d811c2d6dcf785768.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5e4e4666a8b83aee34ddb7b7793de560.png)
更新时间:2018-03-08 07:43:26
|
相似题推荐
解答题-问答题
|
适中
(0.65)
【推荐1】数学阅读:古希腊数学家海伦曾提出一个利用三角形三边之长求面积的公式:若一个三角形的三边长分别为a、b、c,则这个三角形的面积为
,其中
.这个公式称为“海伦公式”.数学应用:如图1,在
中,已知
,
,
.
(1)请运用海伦公式求△ABC的面积;
(2)设
边上的高为
,
边上的高
,求
的值;
(3)如图2,
、
为
的两条角平分线,它们的交点为I,求
的面积.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c667f76da3658f200fff8eadb24b8e82.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a822dd4e1d3859f55874669092697a7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b3c65edad25ddd666cdce0d7e5afefc9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d649afbddd907f0dfec1420f02f82fd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4494a85de0be0b97a69348115aef8513.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dae8221601c7bd5c51fd520615581fa1.png)
(1)请运用海伦公式求△ABC的面积;
(2)设
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/80b53eab97158937f92039c1e133b0f1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f285174fbf90a9742de57c1e53224cff.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/382652d34f3340c6e5b2c762c102b9a4.png)
(3)如图2,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85c4bdfb0db1e31e8459df1d15f9ab55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b3c65edad25ddd666cdce0d7e5afefc9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/707b1af82ad30cc1dbed4cf96a98ebc0.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/9/23/75f1764a-f7ea-47dd-99e0-2306a9fd2892.png?resizew=284)
您最近一年使用:0次
解答题-应用题
|
适中
(0.65)
名校
【推荐2】【阅读下列材料】
我们知道:
,
即
,
(当且仅当
时,
).
进一步得到当
时,![](https://staticzujuan.xkw.com/quesimg/Upload/formula/27d1e1d98b3b363060749bcf5bbb910f.png)
,即
,
(当且仅当
时,
)
【例】若
,求
的最小值.
解:
,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/58ca95517fed50fd91cc07524b1420d3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d50eb7e32ed6aaafc74350fbb60c22e6.png)
的最小值为4.
【解决问题】
(1)当
时,当且仅当
__________时,
有最小值__________.
(2)用篱笆围成一个一面靠墙(墙足够长),面积为
的长方形菜园,当这个长方形的边长为多少时,所用篱笆最短?最短篱笆的长是多少?
我们知道:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9c50ee6d453ad5a650c43a73aa03a311.png)
即
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ea8c62af19011d7171da2e6719c031c4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/288665d21ec2dd86d544054cccdd27b7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1f22fec5a381ae8aca93d876e54c79de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7a72239bfc94ae8a1cf332931d80773b.png)
进一步得到当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2684b72f9f38f5046c8ecd4280b7b14b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/27d1e1d98b3b363060749bcf5bbb910f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5f27f5e6dc31fe191061f8fbab906b8b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1aa17b6e2444b45c86bc6cb78cd917a3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e5236ebaf85f88312d5cc7b9d1d8d08b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1f22fec5a381ae8aca93d876e54c79de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0bb678f363bc992a73134a79f1328775.png)
【例】若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/30c8266712c5eb1363c69f49039de3e1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/20d6fc9b90f370fbb27552876b650f8f.png)
解:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3f2ef64123b3b742ce50cdd5e6ee5c25.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/58ca95517fed50fd91cc07524b1420d3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d50eb7e32ed6aaafc74350fbb60c22e6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/518b6b0afe1781f08e28e1fee934e719.png)
【解决问题】
(1)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08115d6d9f876dea921a4d32260ff1fb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4ec0618ae3a4fde6d6220010af229b9a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/13f40c24c64bbb0645fcf585f4e66872.png)
(2)用篱笆围成一个一面靠墙(墙足够长),面积为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/66f243cca452b1a0b5ecc805c626fdb6.png)
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