Proving satisfiability and validity

Hi,

I am struggling to prove whether the following statements are true or false, and consequently to prove why that is.
Mainly because I don't understand the difference between satisfiable and valid, so if someone could explain that, I'd highly appreciate it!

Re: Proving satisfiability and validity

F is satisfiable if F is true in at least one interpretation. For example, 1 + 1 = 0 is satisfiable because it is true in . F is valid if it is true in all interpetations. For example, 1 + 1 = 0 and 1 + 1 = 2 are not valid, but 1 = 1 is. Obviously, if a formula is valid, it is satisfiable. (This assumes that there is at least one interpretation.)

Concerning the first claim, a stronger one is true: F is satisfiable or ~F is valid for all F.