It’s a reference to the original phrasing of Fermat’s note on said theorem: “It is impossible to separate a cube into two cubes, or a fourth power into two fourth powers, or in general, any power higher than the second, into two like powers. I have discovered a truly marvelous proof of this, which this margin is too narrow to contain.” (It is questionable whether this is true or not.)
It has already been proven.
Of course, but not elegantly.
I believe this was part serious example, part reference to the Laganne(sp?) Omake in HPMoR.
It’s a reference to the original phrasing of Fermat’s note on said theorem: “It is impossible to separate a cube into two cubes, or a fourth power into two fourth powers, or in general, any power higher than the second, into two like powers. I have discovered a truly marvelous proof of this, which this margin is too narrow to contain.” (It is questionable whether this is true or not.)