Lê Anh Duy
01/09/2018 at 16:02-
Alone 23/10/2018 at 13:01
\(x^2+5y^2-4xy-x+2y-6=0\)
\(\Leftrightarrow x^2-4xy+4y^2-\left(x-2y\right)-6=-y^2\)
\(\Leftrightarrow\left(x-2y\right)^2-\left(x-2y\right)-6=-y^2\le0\)
\(\Leftrightarrow\left(x-2y+2\right)\left(x-2y-3\right)\le0\)
\(\Leftrightarrow-2\le x-2y\le3\)
Lê Anh Duy selected this answer.