$\left \{ {{3x -4y =-2 } \atop {5x +2y =14 }} \right.$
⇔$\left \{ {{3x -4y =-2 } \atop {10x+4y=28}} \right.$
⇔$\left \{ {{13x=26⇔x=2} \atop {10+2y=14}} \right.$
⇔$\left \{ {{x=2} \atop {2y=4}} \right.$
⇔$\left \{ {{x=2} \atop {y=2}} \right.$
Vậy...
$\left \{ {{3x +5y =3} \atop { 3x -2y =14}} \right.$
⇔$\left \{ {{7y=-11⇔y=\frac{-11}{7}} \atop {3x+\frac{22}{7}=14}} \right.$
⇔$\left \{ {{y=\frac{-11}{7}} \atop {3x=\frac{76}{7}}} \right.$
⇔$\left \{ {{y=\frac{-11}{7}} \atop {x=\frac{76}{21}}} \right.$
Vậy...
