x=0 thi y=1Voi x#0 thi y=1-$\frac{2x}{x^{2}+x+1}$=1-$\frac{2}{x+1+\frac{1}{x}}$Nhan thay:A=x$+\frac{1}{x}$$\geq$2(Voi x>0)(Co-si 2 so)(x<0 thi A>1 )Vay GTNN cua y la$\frac{1}{3}$$\Leftrightarrow$x=1
x=0 thi y=1Voi x#0 thi y=1-$\frac{2x}{x^{2}+x+1}$=1-$\frac{2}{x+1+\frac{1}{x}}$Nhan thay:A=x$+\frac{1}{x}$$\geq$2(Voi x>0)(Co-si 2 so)(x<0 thi A<0 )Vay GTNN cua y la$\frac{1}{3}$$\Leftrightarrow$x=1
x=0 thi y=1Voi x#0 thi y=1-$\frac{2x}{x^{2}+x+1}$=1-$\frac{2}{x+1+\frac{1}{x}}$Nhan thay:A=x$+\frac{1}{x}$$\geq$2(Voi x>0)(Co-si 2 so)(x<0 thi A&
gt;
1 )Vay GTNN cua y la$\frac{1}{3}$$\Leftrightarrow$x=1