Tìm Min của [tex]25x^{2}+3y^{2}-10x+8y-11[/tex]
[tex]25x^{2}+3y^{2}-10x+8y-11[/tex]
=[tex](25x^{2}-10x+1)+3y^{2}+8y-12[/tex]
= [tex](5x-1)^{2}+ 3(y^{2}+ \frac{8}{3}y-4)[/tex]
=[tex](5x-1)^{2}+ 3(y^{2}+2y.\frac{8}{6}-(\frac{8}{6})^{2}-4-(\frac{8}{6})^{2})[/tex]
=[tex](5x-1)^{2}+ 3((y+\frac{8}{6})^{2}- \frac{52}{9})[/tex]
= [tex](5x-1)^{2}+ 3(y+\frac{8}{6})^{2}-3(\frac{52}{9})[/tex]
mà
(5x-1)^{2}>=0
3(y+\frac{8}{6})^{2}>=0
=> MIn = [tex]\frac{-52}{3}[/tex] khi x= 1/5, y= -8/6