Dmultiplexer truth table and boolean expression
Following is the truth table for a sixteen-to-one demultiplexer.

A0 through A3 are the output address select inputs, and are used to steer the digital input signal on E1 bar to the output corresponding to the port pointed to by the address select inputs, as long as E2 bar is low. 

If you need to construct the Boolean equation for each state, then all you have to do is to collect the terms required to make that state unique and relate them properly.