x² + y² + 4y + 5 = 2x 

x² + y² + 4y + 5 - 2x = 0 

(x² -2x + 1 ) +(y²+ 4y + 4 ) = 0

(x-1)² + (y+2)² = 0 

Vì (x-1)² \(\ge\) 0  ; (y+2)² \(\ge\) 0 

Nên (x-1)² + (y+2)²  \(\ge\) 0

mà (x-1)² + (y+2)²  = 0 

\(\Leftrightarrow\left\{{}\begin{matrix}x-1=0\\y+2=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=1\\y=-2\end{matrix}\right.\) 

Vậy x=1 ; y=-2