This site is to be used only as a learning tool for Dr. Baglama's MTH215 Linear
Answers to Posed Questions
Question 1 Tue Feb 3 12:40:33
Professor, I disagree with the answer provided in the back of the text book for #45. It says that
the two matrices do not commute for any real number, when clearly, if you multiply them (or add
them), and set R = 2, (or any real number in the case of adding), they commute. I have gone over
this many times and tried it in Maple as well. If you set R = 2, you'll end up with a matrix of
[[2,0,2],[0,1,0],[2,0,2]] if you multiply them as A*B or B*A. (Adding results in a matrix of
[[3,0,1],[0,2,0],[1,0,R+1]] both ways). Is there something I'm missing? Thanks!
You are correct, if r=2 the matrices commute, i.e. A*B = B*A. Addition always commutes.
Question 2 Mon Feb 9 13:33:40
I'm not sure how to go about solving problem #25 from section 1.4. Can you
give a hint?
In order for the vector b to be in the span of vectors v1,
v2, and v3 you have to be able to find constants
k1, k2, and k3 such that,
b = k1v1 + k2v2
+ k3v3, which is a vector representation of a linear
Question 3 Tue Feb 10 23:41:09
For those of us who can't make it to the review on Friday, can you please state here, (as specific as
possible) what you'll be covering? We already know that it'll deal with Chapter 1, anything we maybe
should not bother looking over in those sections? Thanks!
I will not give hints for the exam during the review. I will only answer
questions about homework problems, techinques or concepts that we have
already covered in class. Nothing new will be discussed.