[tex]2x^2+6y^2-9y+2x+7=2(x^2+x+\frac{1}{4})+6(y^2-\frac{3}{2}y+\frac{9}{16})+\frac{25}{8}=2(x+\frac{1}{2})^{2}+6(y-\frac{3}{4})+\frac{25}{8}\geq \frac{25}{8}[/tex]
Dấu = xảy ra khi [tex]x=\frac{-1}{2};y=\frac{3}{4}[/tex]
[tex]2x^2+6y^2-9y+2x+7=2(x^2+x+\frac{1}{4})+6(y^2-\frac{3}{2}y+\frac{9}{16})+\frac{25}{8}=2(x+\frac{1}{2})^{2}+6(y-\frac{3}{4})+\frac{25}{8}\geq \frac{25}{8}[/tex]
Dấu = xảy ra khi [tex]x=\frac{-1}{2};y=\frac{3}{4}[/tex]
[tex]2x^2+6y^2-9y+2x+7=2(x^2+x+\frac{1}{4})+6(y^2-\frac{3}{2}y+\frac{9}{16})+\frac{25}{8}=2(x+\frac{1}{2})^{2}+6(y-\frac{3}{4})+\frac{25}{8}\geq \frac{25}{8}[/tex]
Dấu = xảy ra khi [tex]x=\frac{-1}{2};y=\frac{3}{4}[/tex]