Thay \(a=-\sqrt{2}\) vào pt :
\(\left\{{}\begin{matrix}\left(-\sqrt{2}+1\right)x-y=3\left(1\right)\\-\sqrt{2}x+y=-\sqrt{2}\left(2\right)\end{matrix}\right.\)
Lấy \(\left(1\right)+\left(2\right):\)
\(\left(-\sqrt{2}+1-\sqrt{2}\right)x=3-\sqrt{2}\)
\(\Leftrightarrow x=\dfrac{3-\sqrt{2}}{1-2\sqrt{2}}\)
\(\Leftrightarrow x=\dfrac{1-5\sqrt{2}}{7}\)\(\left(3\right)\)
Thay \(\left(3\right)\) vào \(\left(2\right)\) : \(-\sqrt{2}.\dfrac{1-5\sqrt{2}}{7}+y=-\sqrt{2}\)
\(\Rightarrow y=\)\(-\sqrt{2}+\dfrac{6\sqrt{2}}{7}\)
\(\Rightarrow y=-\dfrac{\sqrt{2}}{7}\)
Vậy hệ pt có nghiệm duy nhất \(\left(x;y\right)=\left(\dfrac{1-5\sqrt{2}}{7};-\dfrac{\sqrt{2}}{7}\right)\)
