Answer:
NOT (NOT x AND NOT y)
Explanation:
This is DeMorgan's theorem. Look that up for more details.
[tex]{\displaystyle {\overline {A\cdot B}}={\overline {A}}+{\overline {B}}} \newline \newline{\displaystyle {\overline {A+B}}={\overline {A}}\cdot {\overline {B}}}[/tex]
So
[tex]{A + B}=\overline{{\overline {A}}\cdot{\overline {B}}}}[/tex]
You can also compare them by creating a truth table.
[tex]\begin{tabular}{ c | c | c } x & y & x OR y \\ 0 & 0 & 0 \\ 0 & 1 & 1 \\ 1 & 0 & 1 \\ 1 & 1 & 1 \\\end{tabular}[/tex]
