A Note on Matching Variables to Equations

We showed with J. P. Gollin that if a (possibly infinite) homogeneous linear equation system has only the trivial solution, then there exists an injective function from the variables to the equations such that each variable has non-zero coefficient in its image. Shortly after a more elementary proof was found by Aharoni and Guo. In this note we present a very short matroid-theoretic proof which we believe is the simplest possible proof of this theorem.