Hi, 1. The problem statement, all variables and given/known data I'd like to show that the induced 1-norm satisfies: ∥A∥1=max1≤j≤n∑[i=1 to n] |ai,j| 2. Relevant equations 3. The attempt at a solution I realise the sum ∑[i=1 to n] |ai,j| is basically ||Ax|| where x is the j-th basis. I also know that ||A||1=max||x||1=1||Ax||. And since ||x||1=1, ∑[i=1 to n]|xi|=1. But I am not sure how to assemble all that together. Would anyone please advise?