In this linear algebra problem, we count the roots of a polynomial in the interval \(]-1,1[\).

A probability problem which gives a proof of the Khintchine's inequalities.

A problem about normal law, Student's and \(\chi^2\)'s.

An original problem which studies different models of ferromagnetism.

A proof of the irrationality of \(\zeta(2)=\sum_{n=1}^{+\infty} \frac{1}{n^2}\).