题目

FourFreedoms                                ByFranklin Roosevelt In the future days, which we seek to make secure, we look forward to aworld founded upon four essential human freedoms. The first is freedom of speech and expression—everywhere in the world. The second is freedom of every person to worship (崇拜) God in his own way—everywhere in the world. The third is freedom from want, which, translated into world terms, meanseconomic understandings which will secure to every nation a healthy peacetimelife for its inhabitants—everywhere in the world. T已知与为两个不共线的单位向量，若向量+与向量k-垂直，则实数k=    ．