Tìm GTLN-GTNN:E=x^2+y^2-x+4y+5

Tìm GTLN-GTNN:
E=x^2+y^2-x+4y+5

G=12x-8y-4x^2-y^2+1

H=2x-6y-x^2-y^2-2

K=x^2+10y^2-6xy-10y+26

I=-x^2-4y^2+2x-4y+3