题目内容
设i、j分别是平面直角坐示系Ox,Oy正方向上的单位向量,且![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023211953822938569/SYS201310232119538229385009_ST/0.png)
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023211953822938569/SYS201310232119538229385009_ST/1.png)
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023211953822938569/SYS201310232119538229385009_ST/2.png)
【答案】分析:由A、B、C共线,可找出共线向量,然后由共线向量的性质可解题.
解答:解:
=(n+2)i+(1-m)j,
=(5-n)i+(-2)j.
∵点A、B、C在同一条直线上,∴
∥
,
即
=λ
,
∴(n+2)i+(1-m)j=λ[(5-n)i+(-2)j],
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023211953822938569/SYS201310232119538229385009_DA/6.png)
点评:本题主要考查向量的坐标运算和向量的共线问题.在向量中,共线和平行是相同的.
解答:解:
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023211953822938569/SYS201310232119538229385009_DA/0.png)
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023211953822938569/SYS201310232119538229385009_DA/1.png)
∵点A、B、C在同一条直线上,∴
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023211953822938569/SYS201310232119538229385009_DA/2.png)
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023211953822938569/SYS201310232119538229385009_DA/3.png)
即
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023211953822938569/SYS201310232119538229385009_DA/4.png)
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023211953822938569/SYS201310232119538229385009_DA/5.png)
∴(n+2)i+(1-m)j=λ[(5-n)i+(-2)j],
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023211953822938569/SYS201310232119538229385009_DA/6.png)
点评:本题主要考查向量的坐标运算和向量的共线问题.在向量中,共线和平行是相同的.
![](http://thumb2018.1010pic.com/images/loading.gif)
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