Bonjour,
je bug sur un exercice, pourriez vous m'aider?

c'est la somme de i allant de 0 à n des i^2 i parmi n x^i

Auriez-vous une idée?

Merciiii !

http://latex.codecogs.com/gif.latex?%5Csum_%7Bi%3D0%7D%5En%20i%5E2%20%5Cbinom%7Bn%7D%7Bi%7Dx%5Ei%20%3D%20x%5E2%5Csum_%7Bi%3D0%7D%5En%20i%28i-1%29%20%5Cbinom%7Bn%7D%7Bi%7Dx%5E%7Bi-2%7D%20+%20x%5Csum_%7Bi%3D0%7D%5En%20i%5Cbinom%7Bn%7D%7Bi%7Dx%5E%7Bi-1%7D%20%3D%20x%5E2%5Cfrac%7B%5Cpartial%20%7D%7B%5Cpartial%20x%5E2%7D%5Csum_%7Bi%3D0%7D%5En%5Cbinom%7Bn%7D%7Bi%7Dx%5Ei%20+%20x%5Cfrac%7B%5Cpartial%20%7D%7B%5Cpartial%20x%7D%5Csum_%7Bi%3D0%7D%5En%5Cbinom%7Bn%7D%7Bi%7Dx%5Ei%20%3D%20x%5E2%20n%28n-1%29%281+x%29%5E%7Bn-2%7D%20+%20xn%281+x%29%5E%7Bn-1%7D%20%3D%20nx%28nx+1%29%281+x%29%5E%7Bn-2%7D

de rien