$\left \{ {{2/3x +y=8/3} \atop {3/2x-3y=-9/2}} \right.$ Giải hơt trên bằng phương pháp thế
2 câu trả lời
`{(\frac{2}{3}x+y=\frac{8}{3}),(\frac{3}{2}x-3y=\frac{-9}{2}):}`
`⇔{(y=\frac{8}{3}-\frac{2}{3}x),(\frac{3}{2}x-3.(\frac{8}{3}-\frac{2}{3}x)=\frac{-9}{2}):}`
`⇔{(y=\frac{8}{3}-\frac{2}{3}x),(\frac{3}{2}x-8+2x=\frac{-9}{2}):}`
`⇔{(y=\frac{8}{3}-\frac{2}{3}x),(\frac{7}{2}x=\frac{7}{2}):}`
`⇔{(y=\frac{8}{3}-\frac{2}{3}x),(x=1):}`
`⇔{(y=\frac{8}{3}-\frac{2}{3}),(x=1):}`
`⇔{(x=1),(y=2):}`
Vậy hệ ptr đã cho có nghiệm `(x;y)=(1;2)`