If limn→∞  an-1+n21+n=b, where a is a finite number, then

Limit  =limn→∞     an1+n-1+n21+n  =  limn→∞  a-1n2+an-1n+1            =∞   if   a-1  ≠0If  a-1=0,     limn→∞   an-1n+1=a=b∴   a=b=1