You can't. Parallelograms do not have "point-slope forms". Lines containing segments that are sides of parallelograms have point-slope forms. Be that as it may, the ultimate answer to your question depends a great deal on precisely what information you are given about the parallelogram and that information's relationship to the line segment contained in the line for which you wish to derive an equation.
Please review the rules for posting questions on this site, particularly the one that says: "Ask your question clearly and fully so that it MAKES SENSE. We are not mind readers. We do not have your textbook in front of us. All we know is what you wrote." If the meaning of that rule is not immediately clear, re-read it several times and/or get help from a friend or instructor. And next time lose the "Title Case" in your post, it just looks juvenile and doesn't get you any more or less attention than writing it with proper capitalization.
John
Egw to Beta kai to Sigma
My calculator said it, I believe it, that settles it
