矢量代数问题
问题描述：
矢量代数问题
The position vectors of the points A and B,relative to an origin O,are (3,4) and (k,2k) respectively.
Given that the magnitude of AB is 2,calculate the values of k.
答
（k-3）²+（2k-4）²＝2².
5k²-22k+21＝0.
（k-3）（5k-7）＝0.
k1＝3.k2＝7/5.
兴趣肤阔,千千万人之上;o(≥v≤)o~好棒!