The question is.....

Let u be a solution to Ax = b and v be a solution to Ax = 0, where A is an m x n matrix and b is a vector in R^m. Show that u + v is also a solution to Ax = b.

To be honest, I don't even know where to start. This was a quiz question on a quiz in my linear algebra class. I thought I had gotten it right, or at least mostly correct. But I got no credit for it whats so ever. Please explain how to do this.

TIA

John