Problem statement: show that if Ax = b has a unique solution, then A is invertible.
I have a hint given to me also: suppose Ax = b has a solution and consider that Ay = 0. Deduce y = 0.
I'm not sure how to incorporate this hint into the proof. If someone can help me out, that would be really great. I haven't done mathematical proofs in years while I was working, and now I'm back at school. Any general words of advice on how to start/set up a proof will be greatly appreciated, too! Thanks!