1. Not finding help here? Sign up for a free 30min 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!

Linear algebra question

  1. Dec 3, 2009 #1
    1. The problem statement, all variables and given/known data

    question 1:
    If A is a matrix satisfying 3A^2+6A-I=0, find the inverse of A.

    question 2:
    Let A be a 3x3 matrix with 4A = A^7. Find the possible values det A.

    2. Relevant equations

    none

    3. The attempt at a solution

    this was a very long homework about 17 questions, i solved the others but i got no clue where to start with these, any help is appreciated.

    Best Regards.
     
  2. jcsd
  3. Dec 3, 2009 #2

    Hootenanny

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    HINT: Multiply through by A-1
    HINTs: det(4A) = 4ndet(A) for an nxn matrix. det(A7) = (det(A))7
     
  4. Dec 3, 2009 #3

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    Or, for question 1, note that [itex]3A^2+ 6A= I[/itex] so [itex](3A+ 6)A= I[/itex].
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Linear algebra question
Loading...