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Homework Help: Finding properties of a linear transformation

  1. Mar 22, 2015 #1
    1. The problem statement, all variables and given/known data
    Find the domain, target space, image, rank and nullity of the linear transformation T(A)=Av, where v= (1, 2) and A is any 2×2matrix.

    2. Relevant equations

    3. The attempt at a solution
    I believe I know the domain (R2x2 vector space) and target space (R2), but I am not sure how to solve for the image, rank, and nullity. I have tried making the matrix A an arbitrary 2x2 matrix with the variables a, b, c, d but this doesn't seem to be making it easy to find the image or rank. And I think if I am able to find the rank, I can find the nullity based on the rank-nullity theorem.
  2. jcsd
  3. Mar 22, 2015 #2


    Staff: Mentor

    Not sure what you mean by "R2x2 vector space".
    What does the vector Av look like, using the matrix you described?

    The nullspace is easy: Solve the equation
    $$A\begin{bmatrix} 1 \\ 2 \end{bmatrix} = \begin{bmatrix} 0 \\ 0\end{bmatrix}$$

    Finding the image is similar:
    Solve the equation
    $$A\begin{bmatrix} 1 \\ 2 \end{bmatrix} = \begin{bmatrix} y_1 \\ y_2\end{bmatrix}$$
  4. Mar 22, 2015 #3

    Ok, so if I let
    A= a b
    c d
    then, solving for the nullspace, I would get something like $$t\begin{bmatrix} -2 \\ 0 \end{bmatrix} + s\begin{bmatrix} 0 \\ -0.5\end{bmatrix}$$, meaning $$\begin{bmatrix} -2 \\ 0 \end{bmatrix}, \begin{bmatrix} 0 \\ -0.5\end{bmatrix}$$ spans the nullspace?

    and solving for the image would be similar of course.
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