A=x^2-4xy+5y^2+10x-22y+2017
\(x^2-4xy+4y^2+y^2-2y+1+10\left(x-2y\right)+2016\)=\(\left(x-2y\right)^2+10\left(x-2y\right)+25+\left(y-1\right)^2+2011\)
=\(\left(x-2y+5\right)^2+\left(y-1\right)^2+2011\ge2011\)
=>minA=2011
dau "=" xay ra <=> \(\left\{\begin{matrix}x-2y+5=0\\y=1\end{matrix}\right.\Rightarrow\left\{\begin{matrix}x=-3\\y=1\end{matrix}\right.\)
B=\(x^2+y^2-xy-x-y+1\)
=\(\frac{x^2}{2}-xy+\frac{y^2}{2}+\frac{x^2}{2}-x+\frac{1}{2}+\frac{y^2}{2}+y+\frac{1}{2}\)
=\(\frac{1}{2}\left(x-y\right)^2+\frac{1}{2}\left(x-1\right)^2+\frac{1}{2}\left(y+1\right)^2\)
tự làm nốt nha@@@@@@@@@
