如图,电线杆上有一盏路灯O,电线杆与三个等高的标杆整齐划一地排列在马路的一侧,AB、CD、EF是三个标杆,相邻的两个标杆之间的距离都是2 m,已知AB、CD在灯光下的影长分别为BM=1.6 m,DN=0.6m.
(1)请画出路灯O的位置和标杆EF在路灯灯光下的影子;
(2)求标杆EF的影长.
考点分析:
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(1)把 x
3+2x
2y+y
3+2xy
2在实数范围内因式分解;
(2)已知
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131101185743849628967/SYS201311011857438496289020_ST/0.png)
,求代数式
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131101185743849628967/SYS201311011857438496289020_ST/1.png)
+
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131101185743849628967/SYS201311011857438496289020_ST/2.png)
-2(cos30°)
2的值.
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阅读理【解析】
对于任意正实数a、b,∵
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131101185743849628967/SYS201311011857438496289019_ST/0.png)
≥0,∴
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131101185743849628967/SYS201311011857438496289019_ST/1.png)
≥0,∴a+b≥
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131101185743849628967/SYS201311011857438496289019_ST/2.png)
,只有当a=b时,等号成立.
结论:在a+b≥
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131101185743849628967/SYS201311011857438496289019_ST/3.png)
(a、b均为正实数)中,若ab为定值p,则a+b≥
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131101185743849628967/SYS201311011857438496289019_ST/4.png)
,只有当a=b时,a+b有最小值
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131101185743849628967/SYS201311011857438496289019_ST/5.png)
.
根据上述内容,回答:若m>0,只有当m=
时,
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131101185743849628967/SYS201311011857438496289019_ST/6.png)
有最小值
.
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如果a
2+11a+16=0,b
2+11b+16=0(a≠b),那么
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131101185743849628967/SYS201311011857438496289018_ST/0.png)
的值等于
.
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阅读理【解析】
符号
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131101185743849628967/SYS201311011857438496289016_ST/0.png)
称为二阶行列式,规定它的运算法则为:
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131101185743849628967/SYS201311011857438496289016_ST/1.png)
=ad-bc,例如
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131101185743849628967/SYS201311011857438496289016_ST/2.png)
=3×6-4×5=18-20=-2,请根据阅读理解化简下面的二阶行列式:
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131101185743849628967/SYS201311011857438496289016_ST/3.png)
=
.
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