\(\left\{{}\begin{matrix}5x-6y=17\\9x-y=7\end{matrix}\right.\)
=> \(\left\{{}\begin{matrix}5x-6\left(9x-7\right)=17\\y=9x-7\end{matrix}\right.\)
=> \(\left\{{}\begin{matrix}5x-54x+42=17\\y=9x-7\end{matrix}\right.\)
=> \(\left\{{}\begin{matrix}-49x=-25\\y=9x-7\end{matrix}\right.\)
=> \(\left\{{}\begin{matrix}x=\frac{25}{49}\\y=9\left(\frac{25}{49}\right)-7=\frac{-118}{49}\end{matrix}\right.\)
Vậy hệ phương trình có duy nhất 1 nghiệm là \(\left(x,y\right)=\left(\frac{25}{49};\frac{-118}{49}\right)\) .
