$[A \rightarrow ( B \lor C) ] \land B' \land C' \rightarrow A'$
I know how to read the proof sequence, but I don't know what it means to "justify" each step? Does this mean to just state what each step is doing?
1.) $A \rightarrow (B \lor C)$
4.) $B' \land C'$
5.) $(B \lor C)'$
Not looking for answers, but any guidance is appreciated.