1. The problem statement, all variables and given/known data Need to show that if A is not invertible then exist B (nxn) such that AB=0 but B is different from 0. 2. Relevant equations 3. The attempt at a solution Thought about writing A like E1...Ek*R where Ei are elementary matrices and R(different from I) the row reduced echelon matrice but doesnt seem.to help, any idea??