Driving me nuts !

• Sep 17th 2008, 01:08 PM
Rinor Berisha
Driving me nuts !
Hi Guys. I don't know if this is the right section but I need some explanation on this (plz(Doh)?)

a) Prove that a=b-kc and b=b+ka ($\displaystyle k\neq 1$) are collinear (a,b,c have those lines up that represent vectors)

b) Find $\displaystyle \alpha$ so that vectors a=2i+3j and b=$\displaystyle \alpha$i-j can be collinear.

I know that these are probably simple but my brain isn't really working well.

Any help greatly appreciated.

Rinor
• Sep 17th 2008, 01:45 PM
blertta
b) Find $\displaystyle \alpha$ so that vectors a=2i+3j and b=$\displaystyle \alpha$i-j can be collinear.

I'm not sure but the condition for 2 vectors of beeing collinear is that the coefficient before i and j must be in proportion.
So, math]\alpha[/tex] = 2/3

Hope it's right.
• Sep 17th 2008, 02:33 PM
Rinor Berisha
Quote:

Originally Posted by blertta
b) Find $\displaystyle \alpha$ so that vectors a=2i+3j and b=$\displaystyle \alpha$i-j can be collinear.

I'm not sure but the condition for 2 vectors of beeing collinear is that the coefficient before i and j must be in proportion.
So, math]\alpha[/tex] = 2/3

Hope it's right.

Urmmm.... don't really think so. I have read that $\displaystyle a=\lambda b$, when $\displaystyle \lambda\neq 0$ then that is the case when a and b are collinear, but I fail to apply that on my drill!(Worried)