a:$\overline{X+\overline{Y}}=\overline{X}+\overline{Y}$
b:$\overline{X+Y}=\overline{X}\bullet\overline{Y}$
c:$\left(X+Y\right)\bullet\left(\overline{X}+\overline{Y}\right)=X\overline{Y}+Y\overline{X} $
d:$ \overline{\overline{X}\bullY}=X\bullet\overline{Y} $
e:$\overline{\overline{X}\bullet\overline{Y}}=X\bullY$
1. a b 2. a e 3. b c 4. c d 5. d e