Parallel Vectors: Solving for a

[MozAngeles]

Homework Statement

for what value of a will the vectors u=<2,4,-5> and v=<-4,-8,a>

Homework Equations

(uXv)=0

The Attempt at a Solution

i took the cross product and got 4(a-10)i-2(a-10)j-32k=0

i don't know wher eto go from there do i set a-10=0 solve for a so my answer is ten?

 

[SteamKing]

You didn't finish writing the problem statement.

 

[bmxicle]

Assuming you're trying to find which values of a make the two vectors parralell...

the k-hat component isn't right in what you've posted, and once you get that it's pretty straightforward to find the values of a so that's you get the zero vector as the cross product.

 

[I like Serena]

Hi MozAngeles!

There is an easier way to find 2 parallel vectors.
If u and v are parallel, one must be a multiple of the other.

That is, if you try to solve:

u = λv

that should have a single solution for λ and a.