# Need help with Linear Combinations

Hey all,
im taking geometry and discrete mathematics at my school. Its a 12 U course. And im not doing as well as i would like in it. Im at about a 75, annd i want that to be around 85. So im 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.

## Answers and Replies

D H
Staff Emeritus
Science Advisor
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.

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.

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