1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Can someone check my answer! Thank you!

  1. Mar 25, 2009 #1
    1. The problem statement, all variables and given/known data
    If a 4x4 matrix A with rows v1, v2, v3 and v4 has determinant detA =-2

    then

    then det (v1, 9v2+5v3, 5v2+8v3, v4) =___?


    2. Relevant equations



    3. The attempt at a solution

    Ok, so I think it should be -18 (since 9 x -2). I mean the determinant should not change when adding columns to each other, however multiplying should have an effect, but I am not quite sure what happened to the v3, like do I multiply the determinant by 8, or 5, or none?
     
  2. jcsd
  3. Mar 25, 2009 #2

    Dick

    User Avatar
    Science Advisor
    Homework Helper

    I'll give you a sample, det(v1,9*v2+5*v3,v3,v4)=
    det(v1,9*v2,v3,v4)+det(v1,5*v3,v2,v5)=
    9*det(v1,v2,v3,v4)+5*det(v1,v3,v3,v4). What's that? Now what happens if you put the linear combination in for v3 as well?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook