1已知a=(3,-4),b=(2,3),则2|a|-3ab= 2.已知A(x1,y1),B(x2,y2).则AB向量怎么求.

问题描述:

1已知a=(3,-4),b=(2,3),则2|a|-3ab= 2.已知A(x1,y1),B(x2,y2).则AB向量怎么求.

1已知a=(3,-4),b=(2,3),则2|a|-3ab=2*二次根号下[(3,-4)*(3,-4)]-3*(3,-4)*(2,3)=2*二次根号下[3*3+(-4)*(-4)]-3*[3*2+(,-4)*3]=2*二次根号下25-3*[-6]=2*5+18=282.已知A(x1,y1),B(x2,y2)则AB向量=(x2,y2)-(...