Răspuns:
(3n-1)!*3n*(3n+1)*(3n+2)/(3n-1)!=48*(3n+1)
3n*(3n+1)*(3n+2)=48*(3n+1)
3n*(3n+2)=48
9n²+6n-48=0
∆=36+4*48*9=1764
x=-6+√1764/2*9=-6+42/18=36/18=2
sau x=-6-42/18=-48/18=-24/9
S={-24/9, 2}
