b, \(x^2+6x+5=0\Leftrightarrow\left(x+1\right)\left(x+5\right)=0\Leftrightarrow\left[{}\begin{matrix}x=-1\\x=-5\end{matrix}\right.\)
b, \(x^2+4x+4+y^2+2y+1=0\Leftrightarrow\left(x+2\right)^2+\left(y+1\right)^2=0\)
mà \(\left(x+2\right)^2+\left(y+2\right)^2\ge0\)
Dấu ''='' xảy ra khi x = -2 ; y = -2