Đặt :
[tex]A=\frac{x}{x^2+x+1}=\frac{x^2+2x+1-x^2-x-1}{x^2+x+1}=\frac{(x+1)^2}{x^2+x+1}-1[/tex]
vì [tex]\frac{(x+1)^2}{x^2+x+1}\geq 0 \Rightarrow \frac{(x+1)^2}{x^2+x+1}-1\geq -1[/tex]
Dấu "=" xảy ra khi x=-1.
Vậy Min A=- 1khin x=-1
Đặt :
[tex]A=\frac{x}{x^2+x+1}=\frac{x^2+2x+1-x^2-x-1}{x^2+x+1}=\frac{(x+1)^2}{x^2+x+1}-1[/tex]
vì [tex]\frac{(x+1)^2}{x^2+x+1}\geq 0 \Rightarrow \frac{(x+1)^2}{x^2+x+1}-1\geq -1[/tex]
Dấu "=" xảy ra khi x=-1.
Vậy Min A=- 1khin x=-1