I'm having trouble with one of the questions given as an assignment which is to prove: $$(p\land q)\leftrightarrow(r\land s), \neg r\land q \vdash \neg p$$
I guess I should use proof by contradiction starting with 'assuming $p$'. I haven't really seen biconditional proposition from textbook examples and I can't even find one.
Using biconditional elimination, $$(p\land q)\leftrightarrow(r\land s)$$
is logically equivalent to $$\big((p\land q)\to(r\land s)\big)\land\big((r\land s)\to(p\land q)\big)$$
I can't step forward to next step.