1.在平行四边形ABCD中,AC为对角线,若AB=(2,4) AC=(1,3) 则BD=?2.若a=(1,2) b=(x,1) u=a+2b v=2a-b 且u⊥v 求x的值

问题描述:

1.在平行四边形ABCD中,AC为对角线,若AB=(2,4) AC=(1,3) 则BD=?
2.若a=(1,2) b=(x,1) u=a+2b v=2a-b 且u⊥v 求x的值

1. BD = AD - AB (向量的平行四边形加法法则:AC = AB + AD) = (AC - AB) - AB = AC - 2AB = (1, 3) - 2(2, 4) = (-3, -5)2. u = a + 2b = (1, 2) + 2(x, 1) = (1+2x, 4) v = 2...