Math Is Fun Forum

aqa

Member

Registered: 2011-01-29

Posts: 9

linear algebra , vectors

I am working on the following problem,

Let V1= (-1,2,2) V2 = (1,-1,0) and Y = ( 2,r,-8)

a) determine the value(s) of r for which y belongs to span {V1,V2}

b) give a geometric description of span {V1, V2)

I have calculated a= -4, b=-2 and r=-6, I am not sure what to do next??? I am just starting to learn this material.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,208

Re: linear algebra , vectors

hi aqa,

I agree with your values for 'a',  'b' and  'r'.

V1 and V2 are not parallel so there will be a plane surface going through the origin* that contains them.

Any linear combination of V1 and V2 will be in that plane.

Have a look at

http://www.mathisfunforum.com/viewtopic.php?id=14934

and

http://www.mathisfunforum.com/viewtopic.php?id=14856
(especially diagram on post #20)

*(When you make a linear combination the origin is one possible combination;  a = b = 0.  The diagram mentioned above is for the more general case where the origin is not part of the plane.)

Bob

Last edited by Bob (2011-01-29 22:05:32)

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

aqa

Member

Registered: 2011-01-29

Posts: 9

Re: linear algebra , vectors

Thank you for the responce. It has been over 25 years since I had to study algebra. Due to me becoming disabled, I decided I would go back to school to learn another occupation. I have found that there are very few (1) tutors on campus that know how to do linear agebra. I am glad I found this site.

I will look at the links you provided shortly. I am sure I will have more questions. Once again, Thank You.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,208

Re: linear algebra , vectors

hi aqa,

You are welcome.  Post again, if you need help.

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob