Boolean equation from circuit

Question

Could someone please help me understand what the boolean equation performed by this circuit would be?

Answer 1

Label the output of the first mux X.

Then, create a truth table for X, then Y:

C D X A Y
---------
0 0 1 0 1
0 1 0 0 0
1 0 0 0 0
1 1 1 0 1
0 0 1 1 1
0 1 0 1 1
1 0 0 1 1
1 1 1 1 1

From inspection of the truth table:

Y = A + CD + C'D'