I once failed a Microsoft interview where the biggest strike against me was a question which was just simple algebra, and one that I later saw in some programmi

I once failed a Microsoft interview where the biggest strike against me was a question which was just simple algebra, and one that I later saw in some programming interview book and realized it was actually a fairly simple one. However, my brain froze at the time of the interview. Because I was furious. Because the interviewer kept asking me "Are you sure you have not seen this question before already?" and I kept saying I hadn't. So here is what she was actually conveying a) she does not trust the candidate b) actually having seen the problem before would have made the solution much easier (does it mean not having seen it before would make it that much harder?). Most interestingly, I later saw that the solution basically hinged around a specific insight, in other words it was a fairly binary outcome: you either figured out that little insight, or you didn't. It was not exactly a question which could have been progressively solved, and of course this brilliant interviewer was not moving on to another question either. I should have given the interviewer a piece of my mind, but unfortunately I was brought in for the round of interviews by referral from a friend.