1) lim(n->0) (n+6)(5/6)^n = 6
2) lim(n->∞) (n+6)(5/6)^n
= lim(n->∞) (n+6)/(5/6)^(-n) 用洛必达法则
= lim(n->∞) (5/6)^n/ln1.2
= 0