(4)lim(n->∞) ( n-1)/(n+1)=lim(n->∞) ( 1-1/n)/(1+1/n)=(1-0)/(1+0)=1(6)lim(n->∞) ( 2^n-1)/3^n=lim(n->∞) [ (2/3)^n-(1/3)^n ]=0-0=0
