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求常数a,b.使lim(x->无穷)[(x^2+1)/(x+1)-ax-b]=0

题目详情
求常数a,b.使lim(x->无穷)[(x^2+1)/(x+1)-ax-b]=0
▼优质解答
答案和解析
(x^2+1)/(x+1)-ax-b
=(x^2+1)/(x+1)-(ax+b)(x+1)/(x+1)
=(x^2+1)/(x+1)-[ax^2+(a+b)x+b]/(x+1)
=[(1-a)x^2-(a+b)x+1-b]/(x+1)
若lim(x->无穷)[(x^2+1)/(x+1)-ax-b]=0,则1-a=0且a+b=0.
a=1、b=-1.