Need help with Linear Combinations

[ehjay01]

Hey all,
im taking geometry and discrete mathematics at my school. Its a 12 U course. And I am not doing as well as i would like in it. I am at about a 75, annd i want that to be around 85. So I am looking to you guys for some help. If you guys wouldn't mind awnsering a few questions i have from my homework each night it would be greatly appreciated. The homework doesn't have to be handed in or anything just to improve my knowledge. Thanks.

Homework Statement

11) demonstrate that the three vectors u=(1,3,2) v=(1,-1,1) and w=(5,-1,4) are mutally perpindicular.

12) if vector u=(5,-5,2) vector v=(1,8,-4) and vector w=(-2,-1,2) express vector x=(-3,6,8) in terms of vectors u v and w.

Homework Equations

 

[D H]

11) How do you know whether two vectors are perpendicular to one another?

12) How would you attack a problem like this in general? In other words, what are the relevant equations?

I am not being mean here. You would not learn much if I simply told you the answers. Show us some work and we will help you get past trouble spots.

 

[ehjay01]

11) dot product=0, can i take the first two vectors and use the dot product to see if they are perpindicular, then the second two?
12)my book is at my friends ill edit this when i get it.