I had to look it up... Yes it's basic maths, but it's something which isn't commonly used. It's something I'd expect a mathematician to know, but not your aver

I had to look it up... Yes it's basic maths, but it's something which isn't commonly used. It's something I'd expect a mathematician to know, but not your average member of the public. For an SE, I'd expect them to know binary powers of two and why they're important in computer systems, but negative powers? I can't immediately recall a time I've used them. Frankly, it looks like a pub quiz question, or one thrown in by an interviewer just to be difficult. A bit like a "what does this code do" question which digs into Undefined Behaviour.