Question

已知向量A（3,2),B(-1,2)C(4,1)设向量D（x,y)满足（向量D-C)//(向量A+B)且向量D-C的绝对

Answer 1

D-C = (x-4,y-1)

A+B = (2,4)

(y-1) / (x-4) = 4/2 = 2

y = 2x -7

(x-4)^2 + (y-1)^2 = 1

x = 4+ 根号5 / 5 或 4- 根号5 / 5

y = 1+ 2根号5 / 5 或 1- 2根号5 / 5

D = (4+ 根号5 / 5 ,1+ 2根号5 / 5) 或 (4- 根号5 / 5 ,1- 2根号5 / 5)