1:$X=\overline {A}\cdot \overline {B}+A\cdot B$
2:$X=\overline {A}\cdot B+A\cdot \overline {B}$
3:$X=\left( A+B\right) \cdot \left( A+\overline {B}\right) $
4:$X=\left( \overline {A}+B\right) \cdot \left( A+\overline {B}\right)$
5:$X=\overline {A}\cdot \left( A+B\right) +B\left( \overline {A}+\overline {B}\right)$