Is a constant? Are functions of ?
Hi dw, this seems quite general and probably the reason you can't get started.
Are you are looking for ?
Take a look at posts #8,11,12,13. See if anything you are studying is firmilar.
To Prove it, u is usually a function of x and y i.e. u(x,y). I have no idea what f is but I am thinking it is a function of x and y, f(x,y). A is a linear operator.
To pickslides, I am not sure what I am looking for.
This is the introduction section to Linear Operators.