Lấy ( 1 ) chia ( 2 )
\(\Rightarrow\frac{x}{y}=-\frac{3}{4}\)
\(x=-\frac{3}{4}y\)
Thế vào ( 2 )
\(y\left(-\frac{3}{4}y+y\right)=\frac{1}{9}\)
\(y\left(\frac{1}{4}y\right)=\frac{1}{9}\)
\(\frac{1}{4}y^2=\frac{1}{9}\)
\(y^2=\frac{1}{9}:\frac{1}{4}\)
\(y^2=\frac{4}{9}\)
\(\orbr{\begin{cases}y=\frac{2}{3}\\y=-\frac{2}{3}\end{cases}}\)
TH 1
y = 2/3
\(x=-\frac{3}{4}y=-\frac{3}{4}\cdot\frac{2}{3}=-\frac{1}{2}\)
TH 2
y = -2/3
\(x=-\frac{3}{4}y=-\frac{3}{4}\cdot-\frac{2}{3}=\frac{1}{2}\)