[foobahhhhh]

A => B ≠> A' => B'

[BobaFloutist]

A => B ≠> A' => B' ≠> A' ≠> B'

[foobahhhhh]

Yes that too ... in general of course. ∀ does the heavy lifting.

[BobaFloutist]

I'm a big enough man to admit I'm I haven't seen that one in this semester's Discrete Math.