Re: 2015 permutation X2 marathon
Haven't tried the Q. much, but to find the probability that one random variable is less than another, wouldn't we essentially need to use double integration (at least, this is one way of doing it)?
p² - 4q must be positive.
That is a region on the p-q Cartesian plane.
The restrictions on p and q define a rectangular box on the Cartesian plane.
So you basically just need to find the fraction of the box than contains the above region.
The hitch is the the corner of the box doesn't have to lie on the parabola. So you need two cases - corner inside and corner outside the parabola.
The reason for asking this question is that it leads on to another question which is strongly based on a question in a past Ext 2 HSC exam (it wasn't on probability, but the technique is the same).