若lim[2n+(an^2+2n+1)/(bn+1)=1,则a+b
问题描述：
若lim[2n+(an^2+2n+1)/(bn+1)=1,则a+b
答
lim(n->inf) [2n + (an² + 2n + 1) / (bn + 1)] = 1lim (2bn² + an² + 4n + 1) / (bn + 1) = 1lim [(2b + a)n² + 4n + 1] / (bn + 1) = 12b + a = 0,∵极限趋向常数,分子和分母的最高次方相同,...