Question

If a>b and a(b-a)=0, which one or more of the following must be true?

Answer 1

$a\ \textgreater \ b \Rightarrow a-b\ \textgreater \ 0 \\ \\a(a-b)=0 \Rightarrow a=0 \\ \\a\ \textgreater \ b \\0\ \textgreater \ b \\b\ \textless \ 0$

All options are correct.