quadratic problem. any other method?? 1. Thie problem statement, all variables and given/known data I was solving this question paper and came across the second problem : http://olympiads.hbcse.tifr.res.in/uploads/rmo-2010 [Broken] I wanted to solve this one by calculus. I want to know that, does in problem like this, we may use: If P(x)=Q(x) Then, P'(x)=Q'(x), P''(x)=Q''(x) etc.? I know this equality may not be true for other functions, but is it applicable for this specific problem?