If A -> B is augmented with C, is AC -> B legal? Given the augmentation axiom and the decomposition axioms of functional dependencies and a relation of R(A,B,C) with an FD of:
A -> B

I can augment A -> B with C to get AC -> BC.

Can I then decompose AC -> BC to get AC -> B?
Community wiki answer:

Yes. You can decompose to get AC -&gt; B and AC -&gt; C.