title: Solving intersect and union formula between four sets
body: <p>I am trying to figure out how ( b ^ cd ^ ab ) is converted to ( bc u bd ), can anyone one explain to me how the first formula was converted to the second one?</p>
  
  <p>As shown in the photo below:
  <a href="https://i.stack.imgur.com/TLIX3.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/TLIX3.jpg" alt="enter image description here"></a></p>