f is a real function derivable on [0,1] /f(0)=0 and f(1)=1
prove that ∀n∈N ∃ (x_i )_(1≤i≤n) seqence of reals with x_i ≠x_j if i≠j
and Σ_(k=1) ^n f^′ (x_k )=n.
let f(x) = e^(−x^2 )
1) prove that f^((n)) (x)=p_n (x)e^(−x^2 ) with p_n is a polynom
2) find a relation of recurrence between the p_n
3) calculate p_1 ,p_2 ,p_3 ,p_4