Răspuns:
Explicație pas cu pas:
E(x) =
[tex]x^{3} + x^{2} + 6x + 9 + 2(x^{2} -2^{2} ) -4x -1\\x^{3} +x^{2} +2x+8+2x^{2} -8\\x^{3} +x^{2} +2x+2x^{2} \\x^{3} +3x^{2} +2x\\x(x+1)(x+2)\\E(x) = x(x+1)(x+2) ; E(n) = multiplu 6 =>\\E(n) = n(n+1)(n+2); n = [1 ; +infinit][/tex]
