题目

已知平面向量a,b满足条件 向量a+向量b=(1,0),向量a-向量b=(-1,2),则向量a×向量b等于多少

提问时间：2020-11-02

答案

(a+b)^2=a^2+2ab+b^2=1····························1
(a-b)^2=a^2-2ab+b^2=5 ····························2
1式减2式得：
4ab=-4
解得：ab=-1