If A is a 3x3 matrix and {v1, v2, v3} is a linearly independent set of vectors in R^3 for which {Av1, Av2, Av3} is also a linearly independent set, then the matrix A must be invertible.
Is this true? Can someone please explain why or why not??
I have read a lot but could not find any resources related to this theorem.
I do not have any idea of how to look at this problem.