I'm factoring the difference of two cubes: mx3+my3-x-y,
I get this far
and then I do this
m(x+y)(x2+xy+y2)-1(x+y) to get (m-1)(x+y)(x2+xy+y2) which is wrong.
I've worked out what I should have done (I think!),
The worrying thing is, I don't know WHY I can't do what I did when I went wrong ! So how do I recognise when I'm going to do it again?