长亭送别收尾改写散文:分式最小值?

来源:百度文库 编辑:中科新闻网 时间:2024/05/11 04:49:30
(X^2-x-5)/(x+2)

(x^2-x-5)/(x+2)
=[(x+2)(x-3)+1]/(x+2)
=(x-3)+1/(x+2)
=(x+2)+1/(x+2)-5
≥2-5
=-3

所以最小值是-3

注:题目要限制x>-2

X+2≠0
X≠-2
(X^2-x-5)/(x+2)
=(X-3)(X+2)/(X+2)
=X-3
无最小值