Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Matrix problem

  1. Jan 29, 2009 #1
    Given that AB = BC, and that A is non-singular, prove that B =C.

    I dont know how to do matrices in these forums, so where I write a matrix, I mean (a,b,c,d)

    Given that A = (3,6,1,2) and B = (1,5,0,1), find a matrix C whose elements are all non zero.

    I can easily do the second part of the question. I cannot understand the logic of the second part of the question - we have proved that B=C, how can C now be non equivalent to B?

  2. jcsd
  3. Jan 29, 2009 #2
    Because the assumption in the first question is that A is non-singular
  4. Jan 29, 2009 #3


    User Avatar
    Science Advisor
    Homework Helper

    I think you mean AB=AC. Like VeeEight said, in the first problem A is assumed to be nonsingular. The matrix you gave for A is the second part is singular. Ax=0 for some nonzero vector x. Use that to construct a C.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook