Does anyone know where the marks would come from for the inverse of the 3x3 matrix A? I'm a bit worried as it was 5 marks
This is just a guess going from previous past papers / judgement, but:
M1 mark for use of B M2 mark for 79 or 1/79 seen M3 mark for substituting in k=-3 (maybe, I can't remember 3 days later whether this was it / necessary for this part of the question) A2 for for correct inverse (minus one for each error?)
You didn't have to, you could work out the inverse another way, the det wasn't involved (it's on the FP2 spec).
What you had to do is re-arrange them like this (I can't remember the question exactly so excuse me if 49 isn't the right multiplier, I might have it mixed up with a practise exam I did XD)