若lim[2n+(an^2+2n+1)/(bn+1)=1,则a+b

lim(n->inf) [2n + (an² + 2n + 1) / (bn + 1)] = 1
lim (2bn² + an² + 4n + 1) / (bn + 1) = 1
lim [(2b + a)n² + 4n + 1] / (bn + 1) = 1
2b + a = 0,∵极限趋向常数,分子和分母的最高次方相同,都是n的一次方
lim (4n + 1) / (bn + 1) = 1
lim (4 + 1/n) / (b + 1/n) = 1
(4 + 0) / (b + 0) = 1
b = 4
a = -2b = -8
∴a + b = -8 + 4 = -4

表述好像有点不清楚

若lim(2n (an^2-2n 1)/(bn 2))=1 求a/b的值 纠正一下：你lim(2n 1)/(bn 2))=1 上下除以2 则lim(2 1/n)/(b 2/n)=1 则