Question

函数题目

已知函数y=(x+2)/(x^2+x+1) (x>-2)
(1)求1/y的取值范围
(2)当x为何值时，y取何最大值？

Answer 1

1.
1/y=[x^2+4x+4-3(x+2)+3]/(x+2) (x>-2)
=(x+2)+3/(x+2)-3 (x>-2)

x+2>0

1/y≥2根号3-3

此时：x+2=根号3
x=根号3-2