Then why doesn't the juxtaposition of mc precede the square?
In your chosen book is the example you're pestering moriquende for, and you can't say shit about it.
Another: Keys To Algebra 1-4's answer booklet, page 19, upper right: "book 2, page 9" expands 6(ab)^3^ to 6(ab)(ab)(ab), and immediately after that, expands (6ab)^3^ to (6ab)(6ab)(6ab). The bullshit you made up says they should be equal.