An algorithm with a higher-order big-O can still be faster than one with a
smaller order for small n. That is the case here. These are just dumb and
fast for small systems that involve symbols. But if there are only numbers,
then the existing methods are better. That's why these are included in the
solve directory, not the matrices directory -- when solving equations, it's
not uncommon to have extra symbols. In any case, a check is made to see
whether there are all numbers present, and if so then the normal det method
is used.