Let a = (x1, Y1) and B = (X2, Y2), then the following is a necessary and sufficient condition for a and B to be collinear: there exists a Let a = (x1, Y1) and B = (X2, Y2), then the following are the necessary and sufficient conditions for a and B to be collinear: a = (x1, Y1) and B = (X2, Y2) ① There is a real number λ, such that a = λ B or B = λ a, why is it right

Let a = (x1, Y1) and B = (X2, Y2), then the following is a necessary and sufficient condition for a and B to be collinear: there exists a Let a = (x1, Y1) and B = (X2, Y2), then the following are the necessary and sufficient conditions for a and B to be collinear: a = (x1, Y1) and B = (X2, Y2) ① There is a real number λ, such that a = λ B or B = λ a, why is it right

Collinear then vectors a and B are proportional
So a = λ B or B = λ a

Given vectors a (x1, Y1), B (X2, Y2), |a | = 2, |b | = 3, a * b = - 6, find (x1 + Y1) / (x2 + Y2) =?

Because | a | = 2, | B | = 3, let X1 = 2coaa, Y1 = 2sina, X2 = 3cosb, y2 = 3sinb
Because a * b = 6cosacosb + 6sinasinb = 6cos (a-b) = - 6
So cos (a-b) = - 1. So A-B = 2K π + π
therefore
（X1+Y1)/(X2+Y2)
=2（cosa+sina）/[3（cosb+sinb）]
=2/3 *[sin（a+π/4）/sin（b+π/4）]
=2/3 *[sin（b+2kπ+π+π/4）/sin（b+π/4）]
=2/3 *[-sin（b+π/4）/sin（b+π/4）]
=-2/3.

There are plane vector formulas: a (x1, Y1) B (X2, Y2), A-B = (x1-x2, y1-y2). But there are also a (X3, Y3) B (x4, Y4), vector AB = (x4-x3, y4-y3)
These two formulas make me a bit confused, the new number does not distinguish OTZ
a. B points to quantity a and vector B respectively. I can't understand the first and second floors of Tat.

Are the difference between two vectors, two representations