Sorry for being ambigous.

Let's start over:
The whole expression ((...)(...)) can be simplified if the two partial expressions (inside the braces) differ in just one negated variable.

If the whole expression can be simplified, then the result is the first partial expression without the variable that differs. (So have to pick first partial expression.)

That's why (in these two examples) one output is (cb) and the other one is (bc)